Dictionary-Based Collections

A dictionary is a list of items with the following two rules:

• Each item is a combination of a key and a value. An item can be made of three parts: a key, a value, and a correspondence between them. The correspondence can be represented by the assignment operator: Key=Value. In some environments, the = operator is used. In some others, the : operator is used. Yet in some others, there is no actual operator that joins both sides but you must know that the key and the value go in pair
• As each item is a combination of a key and a value, each key must be unique. The list of items in the dictionary can be very huge, sometimes in the thousands or even millions. Among the items, each key must be distinct from any other key in the dictionary

In some cases, in addition to these two rules, the items should - in some cases must - be ordered. To order the items, the keys are used. Because in most cases a dictionary is made of words, the keys are ordered in alphabetical order. A dictionary can also be made of items whose keys are date values. In this case, the items would be ordered in chronological order.

There are various types of dictionary types of list used in daily life. The word "dictionary" here does not imply the traditional dictionary that holds the words and their meanings in the English language. The concept is applied in various scenarios.

1. Start Microsoft Visual C#
2. Create a new Windows Application named BethesdaCarRental1
3. To add a new form to the project, in the Solution Explorer, right-click BethesdaCarRental1 -> Add -> Windows Form...
4. Set the Name to RentalRates and press Enter
5. Add a ListView to the form and create its Columns as follows:
    

   (Name)	Text	TextAlign	Width
   colCategory	Category		90
   colDaily	Daily	Right
   colWeekly	Weekly	Right
   colMonthly	Monthly	Right
   colWeekend	Weekend	Right

6. Create its Items as follows:
    

   ListViewItem	SubItems	SubItems	SubItems	SubItems
   	Text	Text	Text	Text
   Economy	35.95	32.75	28.95	24.95
   Compact	39.95	35.75	32.95	28.95
   Standard	45.95	39.75	35.95	32.95
   Full Size	49.95	42.75	38.95	35.95
   Mini Van	55.95	50.75	45.95	42.95
   SUV	55.95	50.75	45.95	42.95
   Truck	42.75	38.75	35.95	32.95
   Van	69.95	62.75	55.95	52.95

7. Complete the design of the form as follows:
    
   
8. To add a new form to the application, in the Solution Explorer, right-click BethesdaCarRental1 -> Add -> Windows Form...
9. Set the Name to Employees and click Add
10. From the Toolbox, add a ListView to the form
11. While the new list view is still selected, in the Properties window, click the ellipsis button of the Columns field and create the columns as follows:
     

    (Name)	Text	TextAlign	Width
    colEmployeeNumber	Empl #		45
    colFirstName	First Name		65
    colLastName	Last Name		65
    colFullName	Full Name		140
    colTitle	Title		120
    colHourlySalary	Hourly Salary	Right	75

12. Design the form as follows: 
     

    Control Text Name Other Properties ListView   lvwEmployees Anchor: Top, Bottom, Left, Right FullRowSelect: True GridLines: True View: Details Button New Employee... btnNewEmployee   Button Close btnClose

13. To add another form to the application, in the Solution Explorer, right- click BethesdaCarRental1 -> Add -> Windows Form...
14. Set the Name to EmployeeEditor and click Add
15. Design the form as follows: 
     

    Control Text Name Properties Label &Employee #:     MaskedTextBox   txtEmployeeNumber Mask: 00-000 Modifiers: public Label First Name:     TextBox   txtFirstName Modifiers: public Label Last Name:     TextBox   txtLastName Modifiers: public Label Full Name:     TextBox   txtFullName Enabled: False Modifiers: public Label Title:     TextBox   txtTitle Modifiers: public Label Hourly Salary:     TextBox   txtHourlySalary Modifiers: public TextAlign: Right Button OK btnOK DialogResult: OK Button Cancel btnCancel DialogResult: Cancel Form     AcceptButton: btnOK CancelButton: btnCancel FormBorderStyle: FixedDialog MaximizeBox: False MinimizeBox: False ShowInTaskbar: False

16. Click the Last Name text box
17. In the Properties window, click the Events button and double-click Leave
18. Implement the event as follows:
     

    // This code is used to create and display the customer's full name private void txtLastName_Leave(object sender, EventArgs e) { string strFirstName = txtFirstName.Text; string strLastName = txtLastName.Text; string strFullName; if (strFirstName.Length == 0) strFullName = strLastName; else strFullName = strLastName + ", " + strFirstName; txtFullName.Text = strFullName; }

19. To add a new class to the project, in the Class View, right- click BethesdaCarRental1 -> Add -> Class...
20. Set the Class Name to Employee and click Add
21. Change the Employee.cs file as follows:
     

    using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace BethesdaCarRental1 { [Serializable] public class Employee { public string FirstName; public string LastName; public string Title; public double HourlySalary; public string FullName { get { return LastName + ", " + FirstName; } } // This default constructor says that // the employee is not defined public Employee() { FirstName = "Unknown"; LastName = "Unknown"; Title = "N/A"; HourlySalary = 0.00; } // This constructor completely defines an employee public Employee(string fname, string lname, string title, double salary) { FirstName = fname; LastName = lname; Title = title; HourlySalary = salary; } } }

22. To add a new form to the application, on the main menu, click Project -> Add Windows Forms
23. Set the Name to Customers and press Enter
24. From the Toolbox, add a ListView to the form
25. While the new list view is still selected, in the Properties window, click the ellipsis button of the Columns field and create the columns as follows:
     

    (Name)	Text	Width
    colDrvLicNbr	Driver's Lic. #	100
    colFullName	Full Name	100
    colAddress	Address	160
    colCity	City	100
    colState	State	38
    colZIPCode	ZIPCode

26. Design the form as follows: 
     

    Control Text Name Other Properties ListView   lvwCustomers View: Details GridLines: True FullRowSelect: True Button New Customer... btnNewCustomer   Button Close btnClose

27. To add another form to the application, on the main menu, click Project -> Add Windows Forms
28. Set the Name to CustomerEditor and click Add
29. Design the form as follows: 
     

    Control Text Name Properties Label Driver's Lic. #:     TextBox   txtDrvLicNbr Modifiers: Public Label State:     ComboBox   cbxStates Modifiers: Public Items: AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VT, VA, WA, WV, WI, WY Label Full Name:     TextBox   txtFullName Modifiers: Public Label Address:     TextBox   txtAddress Modifiers: Public Label City:     TextBox   txtCity Modifiers: Public Label ZIP Code:     TextBox   txtZIPCode Modifiers: Public Button OK btnOK DialogResult: OK Button Close btnCancel DialogResult: Cancel Form     AcceptButton: btnOK CancelButton: btnCancel FormBorderStyle: FixedDialog MaximizeBox: False MinimizeBox: False ShowInTaskbar: False

30. To add a new class to the project, in the Class View, right-click BethesdaCarRental1 -> Add -> Class...
31. Set the Class Name to Customer and click Finish
32. Change the Customer.cs file as follows:
     

    using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace BethesdaCarRental1 { [Serializable] public class Customer { public string FullName; public string Address; public string City; public string State; public string ZIPCode; public Customer() { FullName = ""; Address = ""; City = ""; State = ""; ZIPCode = ""; } // This constructor defines a customer public Customer(string fName, string adr, string ct, string ste, string zip) { FullName = fName; Address = adr; City = ct; State = ste; ZIPCode = zip; } } }

33. Save all
34. Copy the following pictures to any folder somewhere on your computer (this is simply an example of preparing the pictures of cars you would include in your database application):
     

    BMW: 335i	Chevrolet Avalanche
    Honda Accord	Mazda Miata
    Chevrolet Aveo	Ford E150XL
    Buick Lacrosse	Honda Civic
    Ford F-150	Mazda Mazda5
    Volvo S40	Land Rover LR3

35. Return to your programming environment
36. To add a new form to the application, in the Solution Explorer, right-click BethesdaCarRental1 -> Add -> Windows Forms
37. Set the Name to CarEditor and click Add
38. Design the form as follows: 
     

    Control Text Name Other Properties Label Text #     TextBox   txtTagNumber   Label Make:     TextBox   txtMake   Label Model:     TextBox   txtModel   Label Year:     TextBox   txtYear   Label Category:     ComboBox   cboCategories DropDownStyle: DropDownList Items: Economy Compact Standard Full Size Mini Van SUV Truck Van PictureBox   pbxCar SizeMode: Zoom CheckBox CD Player chkCDPlayer CheckAlign: MiddleRight CheckBox DVD Player chkDVDPlayer CheckAlign: MiddleRight Button Select Car Picture... btnSelectPicture   CheckBox Available chkAvailable CheckAlign: MiddleRight Label Picture Name lblPictureName   Button Submit btnSubmit   Button Close btnClose DialogResult: Cancel OpenFileDialog (Name): dlgOpen Title: Select Item Picture DefaultExt: jpg Filter: JPEG Files (*.jpg,*.jpeg)|*.jpg|GIF Files (*.gif)|*.gif|Bitmap Files (*.bmp)|*.bmp|PNG Files (*.png)|*.png Form     FormBorderStyle: FixedDialog MaximizeBox: False MinimizeBox: False ShowInTaskbar: False

39. Double-click the Select Car Picture button and implement its event as follows:
     

    private void btnSelectPicture_Click(object sender, EventArgs e) { if (dlgPicture.ShowDialog() == DialogResult.OK) { lblPictureName.Text = dlgPicture.FileName; pbxCar.Image = Image.FromFile(lblPictureName.Text); } }

40. To add a new class to the project, in the Class View, right-click BethedaCarRental1 -> Add -> Class...
41. Set the Class Name to Car and click Add
42. Change the file as follows:
     

    using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace BethesdaCarRental1 { [Serializable] public class Car { public string Make; public string Model; public int Year; public string Category; public bool HasCDPlayer; public bool HasDVDPlayer; public bool IsAvailable; public Car() { Make = ""; Model = ""; Year = 0; Category = ""; HasCDPlayer = false; HasDVDPlayer = false; IsAvailable = false; } public Car(string mk, string mdl, int yr, string cat, bool cd, bool dvd, bool avl) { Make = mk; Model = mdl; Year = yr; Category = cat; HasCDPlayer = cd; HasDVDPlayer = dvd; IsAvailable = avl; } } }

43. To add a new class to the project, in the Class View, right-click BethesdaCarRental -> Add -> Class...
44. Set the Class Name to RentalOrder and press Enter
45. Access the RentalOrder.cs file and change it as follows:
     

    using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace BethesdaCarRental1 { [Serializable] public class RentalOrder { public string EmployeeNumber; // The following flag will allow us to update/know whether // * The car is currently being used by the customer. // That is, if the car has been picked up by the customer // * The customer has brought the car back public string OrderStatus; // Because every car has a tag number // and that tag number will not change // during the lifetime of a car (while the car remains with our // car rental company, we will // use only the tag number here. // The other pieces of information will // be retrieved from the list of cars public string CarTagNumber; // We will identify the customer by the number // and the name on his or her driver's license public string CustomerDrvLicNbr; public string CustomerName; // Although he or she may keep the same driver's // license number for a lifetime, a customer who // rents cars at different times with this company // over months or years may have different addresses. // Therefore, although we will primarily retrieve the // customer's address from the list of customers, // we will give the clerk the ability to change this // information on a rental order. This means that the // same customer could have different information on // different rental orders. // For this reason, each rental order will its own set // of these pieces of information public string CustomerAddress; public string CustomerCity; public string CustomerState; public string CustomerZIPCode; public string CarCondition; public string TankLevel; // This information will be entered when the car is being rented public int MileageStart; // This information will be entered when the car is brought back public int MileageEnd; // This information will be entered when the car is being rented public DateTime DateStart; // This information will be entered when the car is brought back public DateTime DateEnd; public int Days; // This information will be entered when the car is being rented public double RateApplied; // This calculation should occur when the car is brought back public double SubTotal; public double TaxRate; public double TaxAmount; public double OrderTotal; public RentalOrder() { } } }

46. To add a new form to the project, in the Solution Explorer, right-click BethesdaCarRenat1 -> Add -> Windows Form...
47. Set the Name to OrderProcessing and press Enter
48. Design the form as follows:
     

    Control Text Name Other Properties Label Processed By:   AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft Label Employee #:     MaskedTextBox   txtEmployeeNumber Mask: 00-000 Label Employee Name:     TextBox   txtEmployeeName   Label Processed For   AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft Label Driver's Lic #:     TextBox   txtDrvLicNumber   Label Cust Name:     TextBox   txtCustomerName   Label Address:     TextBox   txtCustomerAddress   Label City:     TextBox   txtCustomerCity   Label State:     ComboBox   cbxCustomerStates DropDownStyle: DropDownList Sorted: True Items: AL, AK, AZ, AR, CA, CO, CT, DE, DC, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VT, VA, WA, WV, WI, WY Label ZIP Code     TextBox   txtCustomerZIPCode   Label Car Selected   AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft Label Tag Number:     TextBox   txtTagNumber   Label Car Condition:     ComboBox   cbxCarConditions Sorted: True Items: Needs Repair Drivable Excellent Label Make:     TextBox   txtMake   Label Model:     TextBox   txtModel   Label Year:     TextBox   txtCarYear   label Tank Level:     ComboBox   cbxTankLevels Empty 1/4 Empty 1/2 Full 3/4 Full Full Label Mileage Start:     TextBox   txtMileageStart TextAlign: Right Label Mileage End:     TextBox   txtMileageEnd TextAlign: Right Label Order Timing   AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft Label Start Date:     DateTimePicker   dtpStartDate   Label End Date:     DateTimePicker   dtpEndDate   Label Days:     TextBox 0 txtDays TextAlign: Right Label Order Status     ComboBox   cbxOrderStatus Items: Car On Road Car Returned Order Reserved Label Order Evaluation   AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft Label Rate Applied:     TextBox 0.00 txtRateApplied TextAlign: Right Button Rental Rates btnRentalRates   Label Sub-Total:     TextBox 0.00 txtSubTotal TextAlign: Right Button Calculate btnCalculate   Label Tax Rate:     TextBox 7.75 txtTaxRate TextAlign: Right Label %     Button Save btnSave   Label Tax Amount:     TextBox 0.00 txtTaxAmount TextAlign: Right Button Print... btnPrint   Label Order Total:     TextBox 0.00 txtOrderTotal TextAlign: Right Button Print Preview... btnPrintPreview   Label Receipt #:     TextBox 0 txtReceiptNumber   Button Open btnOpen   Button New Rental Order/Reset btnNewRentalOrder   Button Close btnClose

49. On to the Order Processing form, double-click the Start Date date time picker control
50. Implement the event as follows:
     

    private void dtpStartDate_ValueChanged(object sender, EventArgs e) { dtpEndDate.Value = dtpStartDate.Value; }

51. Return to the Order Processing form and double-click the End Date control
52. Implement its Click event as follows:
     

    // This event approximately evaluates the number of days as a // difference between the end date and the starting date private void dtpEndDate_ValueChanged(object sender, EventArgs e) { int days; DateTime dteStart = this.dtpStartDate.Value; DateTime dteEnd = this.dtpEndDate.Value; // Let's calculate the difference in days TimeSpan tme = dteEnd - dteStart; days = tme.Days; // If the customer returns the car the same day, // we consider that the car was rented for 1 day if (days == 0) days = 1; txtDays.Text = days.ToString(); // At any case, we will let the clerk specify the actual number of days }

53. Return to the Order Processing form and double-click the Rental Rates button
54. Implement its event as follows:
     

    private void btnRentalRates_Click(object sender, EventArgs e) { RentalRates wndRates = new RentalRates(); wndRates.Show(); }

55. Return to the Order Processing form and double-click the Calculate button
56. Implement its event as follows:
     

    private void btnCalculate_Click(object sender, EventArgs e) { int Days = 0; double RateApplied = 0.00; double SubTotal = 0.00; double TaxRate = 0.00; double TaxAmount = 0.00; double OrderTotal = 0.00; try { Days = int.Parse(this.txtDays.Text); } catch (FormatException) { MessageBox.Show("Invalid Number of Days"); } try { RateApplied = double.Parse(txtRateApplied.Text); } catch (FormatException) { MessageBox.Show("Invalid Amount for Rate Applied"); } SubTotal = Days * RateApplied; txtSubTotal.Text = SubTotal.ToString("F"); try { TaxRate = double.Parse(txtTaxRate.Text); } catch (FormatException) { MessageBox.Show("Invalid Tax Rate"); } TaxAmount = SubTotal * TaxRate / 100; txtTaxAmount.Text = TaxAmount.ToString("F"); OrderTotal = SubTotal + TaxAmount; txtOrderTotal.Text = OrderTotal.ToString("F"); }

57. Return to the Order Processing form
58. From the Printing section of the Toolbox, click PrintDocument and click the form
59. In the Properties window, set its (Name) to docPrint and press Enter
60. Under the form, double-click docPrint and implement its event as follows:
     

    private void docPrint_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e) { e.Graphics.DrawLine(new Pen(Color.Black, 2), 80, 90, 750, 90); e.Graphics.DrawLine(new Pen(Color.Black, 1), 80, 93, 750, 93); string strDisplay = "Bethesda Car Rental"; System.Drawing.Font fntString = new Font("Times New Roman", 28, FontStyle.Bold); e.Graphics.DrawString(strDisplay, fntString, Brushes.Black, 240, 100); strDisplay = "Car Rental Order"; fntString = new System.Drawing.Font("Times New Roman", 22, FontStyle.Regular); e.Graphics.DrawString(strDisplay, fntString, Brushes.Black, 320, 150); e.Graphics.DrawLine(new Pen(Color.Black, 1), 80, 187, 750, 187); e.Graphics.DrawLine(new Pen(Color.Black, 2), 80, 190, 750, 190); fntString = new System.Drawing.Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Receipt #: ", fntString, Brushes.Black, 100, 220); fntString = new System.Drawing.Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtReceiptNumber.Text, fntString, Brushes.Black, 260, 220); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 240, 380, 240); fntString = new System.Drawing.Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Processed By: ", fntString, Brushes.Black, 420, 220); fntString = new System.Drawing.Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtEmployeeName.Text, fntString, Brushes.Black, 550, 220); e.Graphics.DrawLine(new Pen(Color.Black, 1), 420, 240, 720, 240); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.FillRectangle(Brushes.Gray, new Rectangle(100, 260, 620, 20)); e.Graphics.DrawRectangle(Pens.Black, new Rectangle(100, 260, 620, 20)); e.Graphics.DrawString("Customer", fntString, Brushes.White, 100, 260); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Driver's License #: ", fntString, Brushes.Black, 100, 300); e.Graphics.DrawString("Name: ", fntString, Brushes.Black, 420, 300); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtDrvLicNumber.Text, fntString, Brushes.Black, 260, 300); e.Graphics.DrawString(txtCustomerName.Text, fntString, Brushes.Black, 540, 300); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 320, 720, 320); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Address: ", fntString, Brushes.Black, 100, 330); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtCustomerAddress.Text, fntString, Brushes.Black, 260, 330); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 350, 720, 350); strDisplay = txtCustomerCity.Text + " " + cbxCustomerStates.Text + " " + txtCustomerZIPCode.Text; fntString = new System.Drawing.Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(strDisplay, fntString, Brushes.Black, 260, 360); e.Graphics.DrawLine(new Pen(Color.Black, 1), 260, 380, 720, 380); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.FillRectangle(Brushes.Gray, new Rectangle(100, 410, 620, 20)); e.Graphics.DrawRectangle(Pens.Black, new Rectangle(100, 410, 620, 20)); e.Graphics.DrawString("Car Information", fntString, Brushes.White, 100, 410); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Tag #: ", fntString, Brushes.Black, 100, 450); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtTagNumber.Text, fntString, Brushes.Black, 260, 450); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 470, 380, 470); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Year: ", fntString, Brushes.Black, 420, 450); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtCarYear.Text, fntString, Brushes.Black, 530, 450); e.Graphics.DrawLine(new Pen(Color.Black, 1), 420, 470, 720, 470); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Make: ", fntString, Brushes.Black, 100, 480); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtMake.Text, fntString, Brushes.Black, 260, 480); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 500, 380, 500); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Model: ", fntString, Brushes.Black, 420, 480); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtModel.Text, fntString, Brushes.Black, 530, 480); e.Graphics.DrawLine(new Pen(Color.Black, 1), 420, 500, 720, 500); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Car Condition: ", fntString, Brushes.Black, 100, 510); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(cbxCarConditions.Text, fntString, Brushes.Black, 260, 510); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 530, 380, 530); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Tank Level: ", fntString, Brushes.Black, 420, 510); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(cbxTankLevels.Text, fntString, Brushes.Black, 530, 510); e.Graphics.DrawLine(new Pen(Color.Black, 1), 420, 530, 720, 530); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Mileage Start:", fntString, Brushes.Black, 100, 540); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtMileageStart.Text, fntString, Brushes.Black, 260, 540); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 560, 380, 560); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Mileage End:", fntString, Brushes.Black, 420, 540); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtMileageEnd.Text, fntString, Brushes.Black, 530, 540); e.Graphics.DrawLine(new Pen(Color.Black, 1), 420, 560, 720, 560); e.Graphics.FillRectangle(Brushes.Gray, new Rectangle(100, 590, 620, 20)); e.Graphics.DrawRectangle(Pens.Black, new Rectangle(100, 590, 620, 20)); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Order Timing Information", fntString, Brushes.White, 100, 590); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Start Date:", fntString, Brushes.Black, 100, 620); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(dtpStartDate.Value.ToString("D"), fntString, Brushes.Black, 260, 620); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 640, 720, 640); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("End Date:", fntString, Brushes.Black, 100, 650); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(dtpEndDate.Value.ToString("D"), fntString, Brushes.Black, 260, 650); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 670, 520, 670); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Days:", fntString, Brushes.Black, 550, 650); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtDays.Text, fntString, Brushes.Black, 640, 650); e.Graphics.DrawLine(new Pen(Color.Black, 1), 550, 670, 720, 670); e.Graphics.FillRectangle(Brushes.Gray, new Rectangle(100, 700, 620, 20)); e.Graphics.DrawRectangle(Pens.Black, new Rectangle(100, 700, 620, 20)); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Order Evaluation", fntString, Brushes.White, 100, 700); StringFormat fmtString = new StringFormat(); fmtString.Alignment = StringAlignment.Far; fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Rate Applied:", fntString, Brushes.Black, 100, 740); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtRateApplied.Text, fntString, Brushes.Black, 300, 740, fmtString); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 760, 380, 760); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Tax Rate:", fntString, Brushes.Black, 420, 740); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtTaxRate.Text, fntString, Brushes.Black, 640, 740, fmtString); e.Graphics.DrawString("%", fntString, Brushes.Black, 640, 740); e.Graphics.DrawLine(new Pen(Color.Black, 1), 420, 760, 720, 760); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Sub-Total:", fntString, Brushes.Black, 100, 770); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtSubTotal.Text, fntString, Brushes.Black, 300, 770, fmtString); e.Graphics.DrawLine(new Pen(Color.Black, 1), 100, 790, 380, 790); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Tax Amount:", fntString, Brushes.Black, 420, 770); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtTaxAmount.Text, fntString, Brushes.Black, 640, 770, fmtString); e.Graphics.DrawLine(new Pen(Color.Black, 1), 420, 790, 720, 790); fntString = new Font("Times New Roman", 12, FontStyle.Bold); e.Graphics.DrawString("Order Total:", fntString, Brushes.Black, 420, 800); fntString = new Font("Times New Roman", 12, FontStyle.Regular); e.Graphics.DrawString(txtOrderTotal.Text, fntString, Brushes.Black, 640, 800, fmtString); e.Graphics.DrawLine(new Pen(Color.Black, 1), 420, 820, 720, 820); }

61. Return to the Order Processing form
62. From the Printing section of the Toolbox, click PrintDialog and click the form
63. In the Properties window, change its Name to dlgPrint
64. Still in the Properties windows, set its Document property to docPrint
65. On the Order Processing form, double-click the Print button and implement its event as follows:
     

    private void btnPrint_Click(object sender, EventArgs e) { if (dlgPrint.ShowDialog() == DialogResult.OK) docPrint.Print(); }

66. Return to the Order Processing form
67. From the Printing section of the Toolbox, click PrintPreviewDialog and click the form
68. In the Properties window, change its (Name) to dlgPrintPreview
69. Still in the Properties windows, set its Document property to docPrint
70. On the Order Processing form, double-click the Print Preview button
71. Implement the event as follows:
     

    private void btnPrintPreview_Click(object sender, EventArgs e) { dlgPrintPreview.ShowDialog(); }

72. In the Solution Explorer, right-click Form1.cs and click Rename
73. Type Central.cs and press Enter twice
74. Design the form as follows:
     

    Control Text Name Button Customers &Rental Orders btnRentalOrders Button C&ars btnCars Button &Employees btnEmployees Button &Customers btnCustomers Button C&lose btnClose

75. Double-click the Rental Orders button and implement its event as follows:
     

    private void btnRentalOrders_Click(object sender, EventArgs e) { OrderProcessing dlgOrder = new OrderProcessing(); dlgOrder.ShowDialog(); }

76. Return to the Central form
77. Double-click the Cars button and implement its event as follows:
     

    private void btnCars_Click(object sender, EventArgs e) { CarEditor dlgCars = new CarEditor(); dlgCars.ShowDialog(); }

78. Return to the Central form
79. Double-click the Employees button and implement its event as follows:
     

    private void btnEmployees_Click(object sender, EventArgs e) { Employees dlgEmployees = new Employees(); dlgEmployees.ShowDialog(); }

80. Return to the Central form
81. Double-click the Customers button and implement its event as follows:
     

    private void btnCustomers_Click(object sender, EventArgs e) { Customers dlgCustomers = new Customers(); dlgCustomers.ShowDialog(); }

82. Return to the Central form
83. Double-click the Close button and implement its event as follows:
     

    private void btnClose_Click(object sender, EventArgs e) { Close(); }

84. Save all

To support dictionary-based lists, the .NET Framework provides various interfaces and classes. The interfaces allow you to create your own dictionary type of collection class. The classes allow you to directly create a dictionary-based list with an already built-in functionality. The NET Framework provides support for dictionary-based collections through two classes: Hashtable and SortedList. Both classes implement:

• The IDictionary: This makes it possible to use the DictionaryEntry class to access a key/value item
• The ICollection: This makes it possible to know the number of items in the list
• The IEnumerable: This makes it possible to use the foreach loop to enumerate the members of the list
• And the ICloneable interfaces.

The Hashtable class implements the ISerializable interface, which makes it possible for the list to be serialized. Still, the SortedList class is marked with the Serializable attribute, which makes it possible to file process its list.

The .NET Framework also provides dictionary-types through generic classes. From the System.Collections.Generic namespace, to create a dictionary type of collection, you can use either the Dictionary, the SortedDictionary, or the SortedList class. The System.Collections.Generic.Dictionary class is equivalent to the System.Collections.Hashtable class. The System.Collections.Generic.SortedList class is equivalent to the System.Collections.SortedList class. The System.Collections.Generic.SortedDictionary class is equivalent to the System.Collections.Generic.SortedList class with some differences in the way both classes deal with memory management.

If you decide to use either the System.Collections.Generic.Dictionary or the System.Collections.Generic.SortedList class, when declaring the variable, you must remember to specify the name of the class whose collection is being created.

Before using a dictionary-type of list, you can declare a variable using one of the constructors of the class. Here is an example:

using System;
using System.Drawing;
using System.Collections;
using System.Windows.Forms;

public class Exercise : Form
{
    public Exercise()
    {
        InitializeComponent();
    }

    void InitializeComponent()
    {
        Text = "Students";
        Load += new EventHandler(StartForm);
    }

    void StartForm(object sender, EventArgs e)
    {
        Hashtable Students = new Hashtable();
    }
}

public class Program
{
    static int Main()
    {
        System.Windows.Forms.Application.Run(new Exercise());
        return 0;
    }
}

In this case, the primary list would be empty.

1. Access the CarEditor form and double-click an unoccupied area of its body
2. Implement the Load event as follows:
    

   using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Runtime.Serialization.Formatters.Binary; namespace BethesdaCarRental1a { public partial class CarEditor : Form { Dictionary<string, Car> lstCars; public CarEditor() { InitializeComponent(); } private void btnSelectPicture_Click(object sender, EventArgs e) { if (dlgPicture.ShowDialog() == DialogResult.OK) { lblPictureName.Text = dlgPicture.FileName; pbxCar.Image = Image.FromFile(lblPictureName.Text); } } private void CarEditor_Load(object sender, EventArgs e) { Car vehicle = new Car(); BinaryFormatter bfmCars = new BinaryFormatter(); // This is the file that holds the list of items string FileName = @"C:\Bethesda Car Rental\Cars.crs"; lblPictureName.Text = "."; if (File.Exists(FileName)) { FileStream stmCars = new FileStream(FileName, FileMode.Open, FileAccess.Read, FileShare.Read); try { // Retrieve the list of cars lstCars = (Dictionary<string, Car>)bfmCars.Deserialize(stmCars); } finally { stmCars.Close(); } } else lstCars = new Dictionary<string, Car>(); } } }

3. Display the Order Processing form
4. Right-click the Order Processing form and click View Code
5. Make the following changes:
    

   using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Runtime.Serialization.Formatters.Binary; namespace BethesdaCarRental1a { public partial class RentalOrders : Form { int ReceiptNumber; SortedList<int, RentalOrder> lstRentalOrders; public RentalOrders() { InitializeComponent(); } . . . No Change } }

6. Save all

To add an item to the list, you can call the Add() method. The syntax of the System.Collections.Hashtable.Add() and the System.Collections.SortedList.Add() methods is:

public virtual void Add(object Key, object Value);

The syntax of the System.Collections.Generic.Dictionary.Add(), the System.Collections.Generic.SortedDictionary.Add(), and the System.Collections.Generic.SortedList.Add() method is:

public void Add(TKey key, TValue value);

As you can see, you must provide the key and the value as the first and second arguments to the method respectively. Here are examples of calling the Add() method:

void StartForm(object sender, EventArgs e)
{
    Hashtable Students = new Hashtable();

    Students.Add("Hermine", "Tolston");
    Students.Add("Patrick", "Donley");
}

When calling the Add() method, you must provide a valid Key argument: it cannot be null. For example, the following code would produce an error:

void StartForm(object sender, EventArgs e)
{
    Hashtable Students = new Hashtable();

    Students.Add("Hermine", "Tolston");
    Students.Add("Patrick", "Donley");
    Students.Add(null, "Hannovers");
}

This would produce:

When adding the items to the list, as mentioned in our introduction, each key must be unique: you cannot have two exact keys. If you try adding a key that exists already in the list, the compiler would throw an ArgumentException exception. Based on this, the following code would not work because, on the third call, a "Patrick" key exists already:

void StartForm(object sender, EventArgs e)
{
    Hashtable Students = new Hashtable();

    Students.Add("Hermine", "Tolston");
    Students.Add("Patrick", "Donley");
    Students.Add("Chrissie", "Hannovers");
    Students.Add("Patrick", "Herzog");
}

This would produce:

This means that, when creating a dictionary type of list, you must define a scheme that would make sure that each key is unique among the other keys in the list.

Besides the Add() method, you can use the indexed property to add an item to the collection. To do this, enter the Key in the square brackets of the property and assign it the desired Value. Here is an example:

void StartForm(object sender, EventArgs e)
{
    Hashtable Students = new Hashtable();

    Students.Add("Hermine", "Tolston");
    Students.Add("Patrick", "Donley");
    Students.Add("Chrissie", "Hannovers");
    Students.Add("Patricia", "Herzog");
    Students["Michael"] = "Herlander";
}

1. Display the CarEditor form
2. On the CarEditor form, double-click the Submit button and implement its Click event as follows:
    

   private void btnSubmit_Click(object sender, EventArgs e) { Car vehicle = new Car(); FileStream stmCars = null; BinaryFormatter bfmCars = new BinaryFormatter(); Directory.CreateDirectory(@"C:\Bethesda Car Rental"); string strFilename = @"C:\Bethesda Car Rental\Cars.crs"; if (txtTagNumber.Text.Length == 0) { MessageBox.Show("You must enter the car's tag number"); return; } if (txtMake.Text.Length == 0) { MessageBox.Show("You must specify the car's manufacturer"); return; } if (txtModel.Text.Length == 0) { MessageBox.Show("You must enter the model of the car"); return; } if (txtYear.Text.Length == 0) { MessageBox.Show("You must enter the year of the car"); return; } // Create a car vehicle.Make = txtMake.Text; vehicle.Model = txtModel.Text; vehicle.Year = int.Parse(txtYear.Text); vehicle.Category = cbxCategories.Text; vehicle.HasCDPlayer = chkCDPlayer.Checked; vehicle.HasDVDPlayer = chkDVDPlayer.Checked; vehicle.IsAvailable = chkAvailable.Checked; // Call the Add method of our collection class to add the car lstCars.Add(txtTagNumber.Text, vehicle); // Save the list stmCars = new FileStream(strFilename, FileMode.Create, FileAccess.Write, FileShare.Write); try { bfmCars.Serialize(stmCars, lstCars); if (lblPictureName.Text.Length != 0) { FileInfo flePicture = new FileInfo(lblPictureName.Text); flePicture.CopyTo(@"C:\Bethesda Car Rental\" + txtTagNumber.Text + flePicture.Extension); } txtTagNumber.Text = ""; txtMake.Text = ""; txtModel.Text = ""; txtYear.Text = ""; cbxCategories.Text = "Economy"; chkCDPlayer.Checked = false; chkDVDPlayer.Checked = false; chkAvailable.Checked = false; lblPictureName.Text = "."; pbxCar.Image = null; } finally { stmCars.Close(); } }

3. Display the Customers form and double-click an unoccupied area of its body
4. Change the file as follows:
    

   using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Runtime.Serialization.Formatters.Binary; namespace BethesdaCarRental1a { public partial class Customers : Form { Dictionary<string, Customer> lstCustomers; public Customers() { InitializeComponent(); } internal void ShowCustomers() { } private void Customers_Load(object sender, EventArgs e) { lstCustomers = new Dictionary<string, Customer>(); BinaryFormatter bfmCustomers = new BinaryFormatter(); // This is the file that holds the list of parts string strFilename = @"C:\Bethesda Car Rental\Customers.crc"; if (File.Exists(strFilename)) { FileStream stmCustomers = new FileStream(strFilename, FileMode.Open, FileAccess.Read, FileShare.Read); try { // Retrieve the list of employees from file lstCustomers = (Dictionary<string, Customer>) bfmCustomers.Deserialize(stmCustomers); } finally { stmCustomers.Close(); } } ShowCustomers(); } } }

5. Return to the Customers form and double-click the New Customer button
6. Implement its event as follows:
    

   private void btnNewCustomer_Click(object sender, EventArgs e) { CustomerEditor editor = new CustomerEditor(); Directory.CreateDirectory(@"C:\Bethesda Car Rental"); if (editor.ShowDialog() == DialogResult.OK) { if (editor.txtDrvLicNbr.Text == "") { MessageBox.Show("You must provide the driver's " + "license number of the customer"); return; } if (editor.txtFullName.Text == "") { MessageBox.Show("You must provide the employee's full name"); return; } string strFilename = @"C:\Bethesda Car Rental\Customers.crc"; Customer cust = new Customer(); cust.FullName = editor.txtFullName.Text; cust.Address = editor.txtAddress.Text; cust.City = editor.txtCity.Text; cust.State = editor.cbxStates.Text; cust.ZIPCode = editor.txtZIPCode.Text; lstCustomers.Add(editor.txtDrvLicNbr.Text, cust); FileStream bcrStream = new FileStream(strFilename, FileMode.Create, FileAccess.Write, FileShare.Write); BinaryFormatter bcrBinary = new BinaryFormatter(); bcrBinary.Serialize(bcrStream, lstCustomers); bcrStream.Close(); ShowCustomers(); } }

7. Display the Employees form and double-click an unoccupied area of its body
8. Change the file as follows:
    

   using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Runtime.Serialization.Formatters.Binary; namespace BethesdaCarRental1a { public partial class Employees : Form { SortedDictionary<string, Employee> lstEmployees; public Employees() { InitializeComponent(); } internal void ShowEmployees() { } private void Employees_Load(object sender, EventArgs e) { lstEmployees = new SortedDictionary<string, Employee>(); BinaryFormatter bfmEmployees = new BinaryFormatter(); // This is the file that holds the list of parts string strFilename = @"C:\Bethesda Car Rental\Employees.cre"; if (File.Exists(strFilename)) { FileStream stmEmployees = new FileStream(strFilename, FileMode.Open, FileAccess.Read, FileShare.Read); try { // Retrieve the list of employees from file lstEmployees = (SortedDictionary<string, Employee>) bfmEmployees.Deserialize(stmEmployees); } finally { stmEmployees.Close(); } } ShowEmployees(); } } }

9. Return to the Employees form and double-click the New Employee button
10. Implement its event as follows:
     

    private void btnNewEmployee_Click(object sender, EventArgs e) { EmployeeEditor editor = new EmployeeEditor(); Directory.CreateDirectory(@"C:\Bethesda Car Rental"); if (editor.ShowDialog() == DialogResult.OK) { if (editor.txtEmployeeNumber.Text == "") { MessageBox.Show("You must provide an employee number"); return; } if (editor.txtLastName.Text == "") { MessageBox.Show("You must provide the employee's last name"); return; } string strFilename = @"C:\Bethesda Car Rental\Employees.cre"; Employee empl = new Employee(); empl.FirstName = editor.txtFirstName.Text; empl.LastName = editor.txtLastName.Text; empl.Title = editor.txtTitle.Text; empl.HourlySalary = double.Parse(editor.txtHourlySalary.Text); lstEmployees.Add(editor.txtEmployeeNumber.Text, empl); FileStream bcrStream = new FileStream(strFilename, FileMode.Create, FileAccess.Write, FileShare.Write); BinaryFormatter bcrBinary = new BinaryFormatter(); bcrBinary.Serialize(bcrStream, lstEmployees); bcrStream.Close(); ShowEmployees(); } }

11. Save all

Although, or because, the key and value are distinct, to consider their combination as a single object, if you are using either the System.Collections.Hasthtable or the System.Collections.SortedList class, the .NET Framework provides the DictionaryEntry structure. To access an item, you can use the foreach loop to visit each item.

To support the foreach loop, the System.Collections.Hashtable and the System.Collections.SortedList classes implement the IEnumerable.GetEnumerator() method. In this case, the item is of type DictionaryEntry: it contains a Key and a Value in combination.

The DictionaryEntry structure contains two properties named Key and Value to identify the components of a combination. Here is an example:

using System;
using System.Drawing;
using System.Collections;
using System.Windows.Forms;

public class Exercise : Form
{
    ListBox lbxStudents;

    public Exercise()
    {
        InitializeComponent();
    }

    void InitializeComponent()
    {
        Text = "Students";
        lbxStudents = new ListBox();
        lbxStudents.Location = new Point(12, 12);
        Controls.Add(lbxStudents);

        Load += new EventHandler(StartForm);
    }

    void StartForm(object sender, EventArgs e)
    {
        Hashtable Students = new Hashtable();

        Students.Add("Hermine", "Tolston");
        Students.Add("Patrick", "Donley");
        Students.Add("Chrissie", "Hannovers");
        Students.Add("Patricia", "Herzog");
        Students["Michael"] = "Herlander";

        foreach (DictionaryEntry entry in Students)
            lbxStudents.Items.Add(entry.Key + " " + entry.Value);
    }
}

This would produce:

If you are using a generic class, the .NET Framework provides the KeyValuePair structure that follows the same functionality as the System.Collections.DictionaryEntry structure, except that you must apply the rules of generic classes.

1. Display the Order Processing form
2. On the form, click the Driver's Lic # text box
3. In the Properties window, click the Events button and, in the Events section, double-click Leave
4. Implement the event as follows:
    

   private void txtDrvLicNumber_Leave(object sender, EventArgs e) { Customer renter = null; string strDrvLicNumber = txtDrvLicNumber.Text; if (strDrvLicNumber.Length == 0) { MessageBox.Show("You must enter the renter's " + "driver's license number"); txtDrvLicNumber.Focus(); return; } Dictionary<string, Customer> lstCustomers = new Dictionary<string, Customer>(); BinaryFormatter bfmCustomers = new BinaryFormatter(); string strFilename = @"C:\Bethesda Car Rental\Customers.crc"; if (File.Exists(strFilename)) { FileStream stmCustomers = new FileStream(strFilename, FileMode.Open, FileAccess.Read, FileShare.Read); try { // Retrieve the list of customers lstCustomers = (Dictionary<string, Customer>) bfmCustomers.Deserialize(stmCustomers); if (lstCustomers.ContainsKey(strDrvLicNumber) == true) { foreach (KeyValuePair<string, Customer> cust in lstCustomers) { if (cust.Key == strDrvLicNumber) { renter = cust.Value; txtCustomerName.Text = renter.FullName; txtCustomerAddress.Text = renter.Address; txtCustomerCity.Text = renter.City; cbxCustomerStates.Text = renter.State; txtCustomerZIPCode.Text = renter.ZIPCode; } } } else { txtCustomerName.Text = ""; txtCustomerAddress.Text = ""; txtCustomerCity.Text = ""; cbxCustomerStates.Text = ""; txtCustomerZIPCode.Text = ""; MessageBox.Show("There is no customer with that driver's " + "license number in our database"); return; } } finally { stmCustomers.Close(); } } }

5. Access the Employees.cs file and implement the ShowEmployees() method as follows:
    

   internal void ShowEmployees() { if( lstEmployees.Count == 0) return; // Before displaying the employees, empty the list view lvwEmployees.Items.Clear(); // This variable will allow us to identify the odd and even indexes int i = 1; // Use the KeyValuePair class to visit each key/value item foreach(KeyValuePair<string, Employee> kvp in lstEmployees ) { ListViewItem lviEmployee = new ListViewItem(kvp.Key); Employee empl = kvp.Value; lviEmployee.SubItems.Add(empl.FirstName); lviEmployee.SubItems.Add(empl.LastName); lviEmployee.SubItems.Add(empl.FullName); lviEmployee.SubItems.Add(empl.Title); lviEmployee.SubItems.Add(empl.HourlySalary.ToString("F")); if( i % 2 == 0 ) { lviEmployee.BackColor = Color.FromArgb(255, 128, 0); lviEmployee.ForeColor = Color.White; } else { lviEmployee.BackColor = Color.FromArgb(128, 64, 64); lviEmployee.ForeColor = Color.White; } lvwEmployees.Items.Add(lviEmployee); i++; } }

6. Access the Customers.cs file and implement the ShowCustomers() method as follows:
    

   internal void ShowCustomers() { if (lstCustomers.Count == 0) return; lvwCustomers.Items.Clear(); int i = 1; foreach (KeyValuePair<string, Customer> kvp in lstCustomers) { ListViewItem lviCustomer = new ListViewItem(kvp.Key); Customer cust = kvp.Value; lviCustomer.SubItems.Add(cust.FullName); lviCustomer.SubItems.Add(cust.Address); lviCustomer.SubItems.Add(cust.City); lviCustomer.SubItems.Add(cust.State); lviCustomer.SubItems.Add(cust.ZIPCode); if (i % 2 == 0) { lviCustomer.BackColor = Color.Navy; lviCustomer.ForeColor = Color.White; } else { lviCustomer.BackColor = Color.Blue; lviCustomer.ForeColor = Color.White; } lvwCustomers.Items.Add(lviCustomer); i++; } }

7. Execute the application
8. Click the Cars button and create the cars
    
9. Close the Car Editor form
10. Click the Customers button then click the New Customer button continually and create a few customers as follows:
     

    Driver's Lic. # State Full Name Address City ZIP Code M-505-862-575 MD Lynda Melman 4277 Jamison Avenue Silver Spring 20904 379-82-7397 DC John Villard 108 Hacken Rd NE Washington 20012 J-938-928-274 MD Chris Young 8522 Aulage Street Rockville 20852 497-22-0614 PA Pamela Ulmreck 12075 Famina Rd Blain 17006 922-71-8395 VA Helene Kapsco 806 Hyena Drive Alexandria 22231 C-374-830-422 MD Hermine Crasson 6255 Old Georgia Ave Silver Spring 20910 836-55-2279 NY Alan Pastore 4228 Talion Street Amherst 14228 397-59-7487 TN Phillis Buster 724 Cranston Circle Knoxville 37919 115-80-2957 FL Elmus Krazucki 808 Rasters Ave Orlando 32810 294-90-7744 VA Helena Weniack 10448 Great Pollard Hwy Arlington 22232

11. Close the Customers form

If you use the System.Collections.Hashtable or the System.Collections.Generic.Dictionary class to create your list, the items are cumulatively added to the collection every time you call the Add() method or when you use the indexed property to add an item. In our introduction, we saw that the optional third rule of a dictionary type of list is that the list be sorted based on the key. To spare you the hassle of manually taking care of this, the alternative is to use the SortedList class.

Whenever a new item is added to a System.Collections.SortedList variable, a System.Collections.Generic.SortedDictionary variable, or a System.Collections.Generic.SortedList variable, the list is rearranged so the collection can be sorted in either alphabetical or chronological order based on the keys. This means that, if you want your list to be logically arranged by the keys, use one of these Sorted classes to create the collection.

1. On the Central form, click the Employees button
2. Create a few employees as follows:
    

   Employee # First Name Last Name Title Hourly Salary 62-845 Patricia Katts General Manager 42.25 92-303 Henry Larson Sales Representative 12.50 25-947 Gertrude Monay Sales Representative 14.05 73-947 Helene Sandt Intern 8.85 40-508 Melanie Karron Sales Representative 12.75 22-580 Ernest Chisen Sales Manager 22.95 20-308 Melissa Roberts Administrative Assistant 15.45

3. Notice that the list of employees is automatically sorted based on the employees numbers.
   Close the forms and return to your programming environment

After adding one or more items to the list, they are stored in two collections. The keys are stored in a collection represented by a property named Keys. The values are stored in the Values property. In the System.Collections classes, the Keys and the Values properties are of type ICollection.

To assist you with managing the keys of their collections, the System.Collections.Generic.Dictionary, the System.Collections.Generic.SortedDictionary, and the System.Collections.Generic.SortedList classes are equipped with a nested class named KeyCollection. KeyCollection is a serializable generic class that implements the ICollection<> interface. The only real functionalities of the nested KeyCollection class are its ability to know the current number of items in the list and the ability to enumerate the members of the collection through a foreach loop.

To assist you with the values of their lists, the System.Collections.Generic.Dictionary, the System.Collections.Generic.SortedDictionary, and the System.Collections.Generic.SortedList classes are equipped with the nested ValueCollection. The ValueCollection serializable class implements the ICollection<> and the IEnumerable interfaces. The functionality of the ValueCollection class is the same as its counterpart of the System.Collections namespace.

1. Display the Order Processing form and double-click the New Rental Order/Reset button
2. Implement the event as follows:
    

   private void btnNewRentalOrder_Click(object sender, EventArgs e) { txtEmployeeNumber.Text = ""; txtEmployeeName.Text = ""; txtDrvLicNumber.Text = ""; txtCustomerName.Text = ""; txtCustomerAddress.Text = ""; txtCustomerCity.Text = ""; cbxCustomerStates.Text = ""; txtCustomerZIPCode.Text = ""; txtTagNumber.Text = ""; cbxCarConditions.Text = ""; txtMake.Text = ""; txtModel.Text = ""; txtCarYear.Text = ""; cbxTankLevels.Text = "Empty"; txtMileageStart.Text = "0"; txtMileageEnd.Text = "0"; dtpStartDate.Value = DateTime.Today; dtpEndDate.Value = DateTime.Today; txtDays.Text = ""; cbxOrderStatus.Text = ""; txtRateApplied.Text = "0.00"; txtSubTotal.Text = "0.00"; txtTaxRate.Text = "7.75"; txtTaxAmount.Text = "0.00"; txtOrderTotal.Text = "0.00"; BinaryFormatter bfmRentalOrders = new BinaryFormatter(); string strFilename = @"C:\Bethesda Car Rental\RentalOrders.cro"; if (File.Exists(strFilename)) { FileStream stmRentalOrders = new FileStream(strFilename, FileMode.Open, FileAccess.Read, FileShare.Read); try { lstRentalOrders = (SortedList<int, RentalOrder>) bfmRentalOrders.Deserialize(stmRentalOrders); ReceiptNumber = lstRentalOrders.Keys[lstRentalOrders.Count - 1] + 1; } finally { stmRentalOrders.Close(); } } else { ReceiptNumber = 100001; lstRentalOrders = new SortedList<int, RentalOrder>(); } txtReceiptNumber.Text = ReceiptNumber.ToString(); }

3. Return to the Order Processing form and double-click an unoccupied area of its body
4. Implement the Load event as follows:
    

   private void OrderProcessing_Load(object sender, EventArgs e) { btnNewRentalOrder_Click(sender, e); }

5. Return to the Order Processing form

Locating an item in a dictionary type of list consists of looking for either a key, a value, or a combination of Key=Value. The Hashtable, the Dictionary, and the SortedList classes are equipped to handle these operations with little effort on your part. If you know the key of an item but want to find a value, you can use the indexed property because it produces it. Here is an example:

void StartForm(object sender, EventArgs e)
{
    Hashtable Students = new Hashtable();

    Students.Add("Hermine", "Tolston");
    Students.Add("Patrick", "Donley");
    Students.Add("Chrissie", "Hannovers");
    Students.Add("Patricia", "Herzog");
    Students["Michael"] = "Herlander";

    foreach (DictionaryEntry entry in Students)
        lbxStudents.Items.Add(entry.Key + " " + entry.Value);

    string Value = (string)Students["Chrissie"];
    MessageBox.Show("The value of the Chrissie key is " + Value);
}

This would produce:

To find out whether a Key/Value item exists in the list, if you are using one of the classes from the System.Collections namespace, you can call the System.Collections.Hashtable.Contains() or the System.Collections.SortedList.Contains() method. Its syntax is:

public virtual bool Contains(object key);

To look for an item, you pass its key as argument to this method. Here is an example:

void StartForm(object sender, EventArgs e)
{
    Hashtable Students = new Hashtable();

    Students.Add("Hermine", "Tolston");
    Students.Add("Patrick", "Donley");
    Students.Add("Chrissie", "Hannovers");
    Students.Add("Patricia", "Herzog");
    Students["Michael"] = "Herlander";

    foreach (DictionaryEntry entry in Students)
        lbxStudents.Items.Add(entry.Key + " " + entry.Value);

     bool found = Students.Contains("Chrissie");

    if (found == true)
        MessageBox.Show("The list contains an item " +
                        "whose key is Chrissie");
    else
        MessageBox.Show("The list doesn't contain an " +
                        "item whose key is Chrissie");

    found = Students.Contains("James");

    if (found == true)
        MessageBox.Show("The list contains an item " +
                        "whose key is James");
    else
        MessageBox.Show("The list doesn't contain an " +
                        "item whose key is James");
}

This would produce:

We have seen that the System.Collections.Hashtable.Contains() and the System.Collections.SortedList.Contains() methods allow you to find out whether a collection contains a certain specific key. An alternative is to call a method named ContainsKey.

The syntax of the System.Collections.Hashtable.ContainsKey() and the System.Collections.SortedList.ContainsKey() method is:

public virtual bool ContainsKey(object key);

The syntax of the System.Collections.Generic.Dictionary.ContainsKey() and the System.Collections.Generic.SortedList.ContainsKey() method is:

public bool ContainsKey(TKey key);

1. On the Order Processing form, double-click the Save button and implement its event as follows:
    

   private void btnSave_Click(object sender, EventArgs e) { if (txtReceiptNumber.Text == "") { MessageBox.Show("The receipt number is missing"); return; } // Don't save this rental order if we don't // know who processed it if (txtEmployeeNumber.Text == "") { MessageBox.Show("You must enter the employee number or the " + "clerk who processed this order."); return; } // Don't save this rental order if we don't // know who is renting the car if (txtDrvLicNumber.Text == "") { MessageBox.Show("You must specify the driver's license number " + "of the customer who is renting the car"); return; } // Don't save the rental order if we don't // know what car is being rented if (txtTagNumber.Text == "") { MessageBox.Show("You must enter the tag number " + "of the car that is being rented"); return; } // Create a rental order based on the information on the form RentalOrder CurrentOrder = new RentalOrder(); CurrentOrder.EmployeeNumber = txtEmployeeNumber.Text; CurrentOrder.OrderStatus = cbxOrderStatus.Text; CurrentOrder.CarTagNumber = txtTagNumber.Text; CurrentOrder.CustomerDrvLicNbr = txtDrvLicNumber.Text; CurrentOrder.CustomerName = txtCustomerName.Text; CurrentOrder.CustomerAddress = txtCustomerAddress.Text; CurrentOrder.CustomerCity = txtCustomerCity.Text; CurrentOrder.CustomerState = cbxCustomerStates.Text; CurrentOrder.CustomerZIPCode = txtCustomerZIPCode.Text; CurrentOrder.CarCondition = cbxCarConditions.Text; CurrentOrder.TankLevel = cbxTankLevels.Text; try { CurrentOrder.MileageStart = int.Parse(txtMileageStart.Text); } catch (FormatException) { MessageBox.Show("Invalid mileage start value"); } try { CurrentOrder.MileageEnd = int.Parse(txtMileageEnd.Text); } catch (FormatException) { MessageBox.Show("Invalid mileage end value"); } try { CurrentOrder.DateStart = dtpStartDate.Value; } catch (FormatException) { MessageBox.Show("Invalid start date"); } try { CurrentOrder.DateEnd = dtpEndDate.Value; } catch (FormatException) { MessageBox.Show("Invalid end date"); } try { CurrentOrder.Days = int.Parse(txtDays.Text); } catch (FormatException) { MessageBox.Show("Invalid number of days"); } try { CurrentOrder.RateApplied = double.Parse(txtRateApplied.Text); } catch (FormatException) { MessageBox.Show("Invalid rate value"); } CurrentOrder.SubTotal = double.Parse(txtSubTotal.Text); try { CurrentOrder.TaxRate = double.Parse(txtTaxRate.Text); } catch (FormatException) { MessageBox.Show("Inavlid tax rate"); } CurrentOrder.TaxAmount = double.Parse(txtTaxAmount.Text); CurrentOrder.OrderTotal = double.Parse(txtOrderTotal.Text); // The rental order is ready // Get the receipt number from its text box try { ReceiptNumber = int.Parse(txtReceiptNumber.Text); } catch (FormatException) { MessageBox.Show("You must provide a receipt number"); } // Get the list of rental orders and // check if there is already one with the current receipt number // If there is already a receipt number like that... if (lstRentalOrders.ContainsKey(ReceiptNumber) == true) { // Simply update its value lstRentalOrders[ReceiptNumber] = CurrentOrder; } else { // If there is no order with that receipt, // then create a new rental order lstRentalOrders.Add(ReceiptNumber, CurrentOrder); } // The list of rental orders string strFilename = @"C:\Bethesda Car Rental\RentalOrders.cro"; FileStream bcrStream = new FileStream(strFilename, FileMode.Create, FileAccess.Write, FileShare.Write); BinaryFormatter bcrBinary = new BinaryFormatter(); try { bcrBinary.Serialize(bcrStream, lstRentalOrders); } finally { bcrStream.Close(); } }

2. Save the file

To find out whether a particular value exists in the list, you can call the ContainsValue() method. The syntax of the System.Collections.Hashtable.ContainsValue() and the System.Collections.SortedList.ContainsValue() method is::

public virtual bool ContainsValue(object key);

The syntax of the System.Collections.Generic.Dictionary.ContainsValue() and the System.Collections.Generic.SortedList.ContainsValue() method is:

public bool ContainsValue(TKey key);

The ContainsKey() method allows you to only find out whether a dictionary-based collection contains a certain key. It does not identify that key and it does not give any significant information about that key, except its existence. In some operations, first you may want to find out if the collection contains a certain key. Second, if that key exists, you may want to get its corresponding value.

To assist you with both checking the existence of a key and getting its corresponding value, the generic Dictionary, SortedDictionary, and SortedList classes are equipped with a method named TryGetValue. Its syntax is:

public bool TryGetValue(TKey key, out TValue value);

When calling this method, the first argument must be the key to look for. If that key is found, the method returns its corresponding value as the second argument passed as an out reference.

1. On the Order Processing form, click the Employee Number text box
2. In the Events section of the Properties window, double-click Leave and implement the event as follows:
    

   private void txtEmployeeNumber_Leave(object sender, EventArgs e) { Employee clerk; string strEmployeeNumber = txtEmployeeNumber.Text; if (strEmployeeNumber.Length == 0) { MessageBox.Show("You must enter the employee's number"); txtEmployeeNumber.Focus(); return; } SortedDictionary<string, Employee> lstEmployees = new SortedDictionary<string, Employee>(); BinaryFormatter bfmEmployees = new BinaryFormatter(); string strFilename = @"C:\Bethesda Car Rental\Employees.cre"; if (File.Exists(strFilename)) { FileStream stmEmployees = new FileStream(strFilename, FileMode.Open, FileAccess.Read, FileShare.Read); try { // Retrieve the list of employees lstEmployees = (SortedDictionary<string, Employee>) bfmEmployees.Deserialize(stmEmployees); if (lstEmployees.TryGetValue(strEmployeeNumber, out clerk)) { txtEmployeeName.Text = clerk.FullName; } else { txtEmployeeName.Text = ""; MessageBox.Show("There is no employee with that number"); return; } } finally { stmEmployees.Close(); } } }

3. Return to the Order Processing form and click the Tag Number text box
4. In the Events section of the Properties window, double-click Leave and implement the event as follows:
    

   private void txtTagNumber_Leave(object sender, EventArgs e) { Car selected; string strTagNumber = txtTagNumber.Text; if (strTagNumber.Length == 0) { MessageBox.Show("You must enter the car's tag number"); txtTagNumber.Focus(); return; } Dictionary<string, Car> lstCars = new Dictionary<string, Car>(); BinaryFormatter bfmCars = new BinaryFormatter(); string strFilename = @"C:\Bethesda Car Rental\Cars.crs"; if (File.Exists(strFilename)) { FileStream stmCars = new FileStream(strFilename, FileMode.Open, FileAccess.Read, FileShare.Read); try { // Retrieve the list of employees from file lstCars = (Dictionary<string, Car>) bfmCars.Deserialize(stmCars); if (lstCars.TryGetValue(strTagNumber, out selected)) { txtMake.Text = selected.Make; txtModel.Text = selected.Model; txtCarYear.Text = selected.Year.ToString(); } else { txtMake.Text = ""; txtModel.Text = ""; txtCarYear.Text = ""; MessageBox.Show("There is no car with that tag " + "number in our database"); return; } } finally { stmCars.Close(); } } }

5. Display the Order Processing form and double-click the Open button
6. Implement its event as follows:
     

   private void btnOpen_Click(object sender, EventArgs e) { RentalOrder order = null; if (txtReceiptNumber.Text == "") { MessageBox.Show("You must enter a receipt number"); return; } ReceiptNumber = int.Parse( txtReceiptNumber.Text); if (lstRentalOrders.TryGetValue(ReceiptNumber, out order)) { txtEmployeeNumber.Text = order.EmployeeNumber; txtEmployeeNumber_Leave(sender, e); cbxOrderStatus.Text = order.OrderStatus; txtTagNumber.Text = order.CarTagNumber; txtTagNumber_Leave(sender, e); txtDrvLicNumber.Text = order.CustomerDrvLicNbr; txtCustomerName.Text = order.CustomerName; txtCustomerAddress.Text = order.CustomerAddress; txtCustomerCity.Text = order.CustomerCity; cbxCustomerStates.Text = order.CustomerState; txtCustomerZIPCode.Text = order.CustomerZIPCode; cbxCarConditions.Text = order.CarCondition; cbxTankLevels.Text = order.TankLevel; txtMileageStart.Text = order.MileageStart.ToString(); txtMileageEnd.Text = order.MileageEnd.ToString(); dtpStartDate.Value = order.DateStart; dtpEndDate.Value = order.DateEnd; txtDays.Text = order.Days.ToString(); txtRateApplied.Text = order.RateApplied.ToString("F"); txtSubTotal.Text = order.SubTotal.ToString("F"); txtTaxRate.Text = order.TaxRate.ToString("F"); txtTaxAmount.Text = order.TaxAmount.ToString("F"); txtOrderTotal.Text = order.OrderTotal.ToString("F"); } else { MessageBox.Show("There is no rental order with that receipt number"); return; } }

7. Return to the Order Processing form
8. Double-click the Close button and implement the event as follows:
    

   private void btnClose_Click(object sender, EventArgs e) { Close(); }

9. Execute the application
10. Create a few rental orders and print them
     
11. Close the forms and return to your programming environment
12. Execute the application again
13. Open a previously created order to simulate a customer returning a car and change some values on the form such as the return date, the mileage end, and the order status
14. Also click the Calculate button to get the final evaluation
     
15. Print the rental orders
16. Close the forms and return to your programming environment

To delete one item from the list, you can call the Remove() method. Its syntax is:

public virtual void Remove(object key);

Here is an example:

using System;
using System.Drawing;
using System.Collections;
using System.Windows.Forms;

public class Exercise : Form
{
    ListBox lbxStudents;
    Button btnRemove;
    Hashtable Students;

    public Exercise()
    {
        InitializeComponent();
    }

    void InitializeComponent()
    {
        Text = "Students";
        lbxStudents = new ListBox();
        lbxStudents.Location = new Point(12, 12);
        Controls.Add(lbxStudents);

        btnRemove = new Button();
        btnRemove.Text = "&Remove";
        btnRemove.Location = new Point(12, lbxStudents.Top + lbxStudents.Height + 10);
        btnRemove.Click += new EventHandler(RemoverClick);
        Controls.Add(btnRemove);

        Load += new EventHandler(StartForm);
    }

    void StartForm(object sender, EventArgs e)
    {
        Students = new Hashtable();

        Students.Add("Hermine", "Tolston");
        Students.Add("Patrick", "Donley");
        Students.Add("Chrissie", "Hannovers");
        Students.Add("Patricia", "Herzog");
        Students["Michael"] = "Herlander";
        Students["Philemon"] = "Jacobs";
        Students["Antoinette"] = "Malhoun";

        foreach (DictionaryEntry entry in Students)
            lbxStudents.Items.Add(entry.Key + " " + entry.Value);
    }

    void RemoverClick(object sender, EventArgs e)
    {
        Students.Remove("Chrissie");

        lbxStudents.Items.Clear();
        foreach (DictionaryEntry entry in Students)
            lbxStudents.Items.Add(entry.Key + " " + entry.Value);
    }
}

This would produce:

To delete all items from the list, you can call the Clear() method. Its syntax is:

public virtual void Clear();

1. Create a Windows Application named BethesdaCarRental1a
   When writing any code that has to do with lists, use a class from the System.Collections namespace
2. Create a class named Employee that will hold the following pieces of information about each employee: the employee number, the date hired, the first name, the middle name, the last name, the home address, the city, the state, the ZIP (or postal) code, the marital status, the title, the email address, the home telephone number, the cell phone number, the work telephone number, the extension, and the hourly salary
3. Create a form named EmployeeEditor and design it so that it includes:
   1. A text box for the employee number, the date hired, the first name, the middle name, the last name, the home address, the city, the ZIP (or postal) code, the title, the email address, the home telephone number, the cell phone number, the work telephone number, the extension, and the hourly salary
   2. A combo box for the state (the items must include all US states and all Canadian provinces in 2-letter abbreviation each), the marital status (the items will include Single no Children, Single Parent, Married no Children, Married With Children, Separated, Widow, Other)
4. Create a form named Employees and that will be used to show some information about each employee of the company, including the employee number, the date hired, the full name (it will consist of the last name, followed by a comma, followed by the first name), the marital status, the title, and the hourly salary.