Lesson 13: XML Reading and Writing

	XML Reading and Writing

Fundamentals of Writing to an XML File

Introduction

In previous lessons, we learned to process XML files using the Document Object Model as implemented by the XmlDocument class. To go further and make XML friendlier, the .NET Framework provides many other classes for different purposes, allowing you to create and manage nodes from custom .NET classes.

Practical Learning: Introducing XML-Based Applications

Start Microsoft Visual Studio .NET and create a Windows Forms Application named CollegeParkAutoRepair1
In the Solution Explorer, right-click Form1.vb and click Rename
Type CPAR.vb and press Enter
From the Menus & Toolbars section of the Toolbox, click MenuStrip and click the form

Design the menu items as follows:

MenuItem		DropDownItems
Text	Name	Text	Name	Shortcut
&File	mnuFile	&New Repair Order	mnuFileNew	Ctrl+N
		&Open Existing Order...	mnuFileOpen	Ctrl+O
		&Save Current Order	mnuFileSave	Ctrl+S
		Separator
		&Print...	mnuFilePrint	Ctrl+P
		Print Pre&view...	mnuFilePrintPreview
		Separator
		E&xit	mnuFileExit

Design the form as follows:

Control	Name	Text	Other Properties
Group		Order Identification
Label		Customer Name:
TextBox	txtCustomerName
Label		Address
TextBox	txtAddress
Label		City:
TextBox	txtCity
Label		State:
TextBox	txtState
Label		ZIP Code:
TextBox	txtZIPCode		TextAlign: Right
Label		Make / Model:
TextBox	txtMake
TextBox	txtModel
Label		Year:
TextBox	txtCarYear		TextAlign: Right
Label		Problem Description:
TextBox	txtProblem
GroupBox		Parts Used
Label		Part Name
Label		Unit Price
Label		Qty
Label		Sub Total
TextBox	txtPartName1
TextBox	txtUnitPrice1	0.00	TextAlign: Right
TextBox	txtQuantity1	0	TextAlign: Right
TextBox	txtSubTotal1	0.00	TextAlign: Right Enabled: False
TextBox	txtPartName2
TextBox	txtUnitPrice2	0.00	TextAlign: Right
TextBox	txtQuantity2	0	TextAlign: Right
TextBox	txtSubTotal2	0.00	TextAlign: Right Enabled: False
TextBox	txtPartName3
TextBox	txtUnitPrice3	0.00	TextAlign: Right
TextBox	txtQuantity3	0	TextAlign: Right
TextBox	txtSubTotal3	0.00	TextAlign: Right Enabled: False
TextBox	txtPartName4
TextBox	txtUnitPrice4	0.00	TextAlign: Right
TextBox	txtQuantity4	0	TextAlign: Right
TextBox	txtSubTotal4	0.00	TextAlign: Right Enabled: False
TextBox	txtPartName5
TextBox	txtUnitPrice5	0.00	TextAlign: Right
TextBox	txtQuantity5	0	TextAlign: Right
TextBox	txtSubTotal5	0.00	TextAlign: Right Enabled: False
GroupBox		Jobs Performed
Label		Price
TextBox	txtJobPerformed1
TextBox	txtJobPrice1	0.00	TextAlign: Right
TextBox	txtJobPerformed2
TextBox	txtJobPrice2	0.00	TextAlign: Right
TextBox	txtJobPerformed3
TextBox	txtJobPrice3	0.00	TextAlign: Right
TextBox	txtJobPerformed4
TextBox	txtJobPrice4	0.00	TextAlign: Right
TextBox	txtJobPerformed5
TextBox	txtJobPrice5	0.00	TextAlign: Right
GroupBox		Order Summary
Label		Total Parts:
TextBox	txtTotalParts	0.00	TextAlign: Right
Label		Total Labor:
TextBox	txtTotalLabor	0.00	TextAlign: Right
Label		Tax Rate:
TextBox	txtTaxRate	7.75	TextAlign: Right
Label		%
Label		Tax Amount:
TextBox	txtTaxAmount	0.00	TextAlign: Right
Label		Total Order:
TextBox	txtTotalOrder	0.00	TextAlign: Right
Label		Recommendations
TextBox	txtRecommendations		Multiline: True ScrollBars: Vertical

Right-click the form and click View Code

Just above the Public Class CPAR line, import the following namespaces:

Imports System.IO
Imports System.Xml
Imports System.Text

Public Class CPAR

End Class

Under the Public Class CPAR line, create a sub-procedure named Calculate as follows:

Imports System.IO
Imports System.Xml

Public Class CPAR
    Private Sub Calculate()
        Dim UnitPricePart1 As Double, UnitPricePart2 As Double
        Dim UnitPricePart3 As Double, UnitPricePart4 As Double
        Dim UnitPricePart5 As Double
        Dim SubTotalPart1 As Double, SubTotalPart2 As Double
        Dim SubTotalPart3 As Double, SubTotalPart4 As Double
        Dim SubTotalPart5 As Double, TotalParts As Double
        Dim QuantityPart1 As Integer, QuantityPart2 As Integer
        Dim QuantityPart3 As Integer, QuantityPart4 As Integer
        Dim QuantityPart5 As Integer
        Dim Job1Price As Double, Job2Price As Double
        Dim Job3Price As Double, Job4Price As Double
        Dim Job5Price As Double, TotalLabor As Double
        Dim TaxRate As Double, TaxAmount As Double
        Dim TotalOrder As Double

        ' Don't charge a part unless it is clearly identified
        If txtPartName1.Text = "" Then
            txtUnitPrice1.Text = "0.00"
            txtQuantity1.Text = "0"
            txtSubTotal1.Text = "0.00"
            UnitPricePart1 = 0.0
        Else
            Try
                UnitPricePart1 = CDbl(txtUnitPrice1.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Unit Price")
                txtUnitPrice1.Text = "0.00"
                txtUnitPrice1.Focus()
            End Try

            Try
                QuantityPart1 = CInt(txtQuantity1.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Quantity")
                txtQuantity1.Text = "0"
                txtQuantity1.Focus()
            End Try
        End If

        If txtPartName2.Text = "" Then
            txtUnitPrice2.Text = "0.00"
            txtQuantity2.Text = "0"
            txtSubTotal2.Text = "0.00"
            UnitPricePart2 = 0.0
        Else
            Try
                UnitPricePart2 = CDbl(txtUnitPrice2.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Unit Price")
                txtUnitPrice2.Text = "0.00"
                txtUnitPrice2.Focus()
            End Try

            Try
                QuantityPart2 = CInt(txtQuantity2.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Quantity")
                txtQuantity2.Text = "0"
                txtQuantity2.Focus()
            End Try
        End If

        If txtPartName3.Text = "" Then
            txtUnitPrice3.Text = "0.00"
            txtQuantity3.Text = "0"
            txtSubTotal3.Text = "0.00"
            UnitPricePart3 = 0.0
        Else
            Try
                UnitPricePart3 = CDbl(txtUnitPrice3.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Unit Price")
                txtUnitPrice3.Text = "0.00"
                txtUnitPrice3.Focus()
            End Try

            Try
                QuantityPart3 = CInt(txtQuantity3.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Quantity")
                txtQuantity3.Text = "0"
                txtQuantity3.Focus()
            End Try
        End If

        If txtPartName4.Text = "" Then
            txtUnitPrice4.Text = "0.00"
            txtQuantity4.Text = "0"
            txtSubTotal4.Text = "0.00"
            UnitPricePart4 = 0.0
        Else
            Try
                UnitPricePart4 = CDbl(txtUnitPrice4.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Unit Price")
                txtUnitPrice4.Text = "0.00"
                txtUnitPrice4.Focus()
            End Try

            Try
                QuantityPart4 = CInt(txtQuantity4.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Quantity")
                txtQuantity4.Text = "0"
                txtQuantity4.Focus()
            End Try
        End If

        If txtPartName5.Text = "" Then
            txtUnitPrice5.Text = "0.00"
            txtQuantity5.Text = "0"
            txtSubTotal5.Text = "0.00"
            UnitPricePart5 = 0.0
        Else
            Try
                UnitPricePart5 = CDbl(txtUnitPrice5.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Unit Price")
                txtUnitPrice5.Text = "0.00"
                txtUnitPrice5.Focus()
            End Try

            Try
                QuantityPart5 = CInt(txtQuantity5.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Quantity")
                txtQuantity5.Text = "0"
                txtQuantity5.Focus()
            End Try
        End If

        ' Don't bill the customer for a job that is not specified
        If txtJobDescription1.Text = "" Then
            txtJobPrice1.Text = "0.00"
            Job1Price = 0.0
        Else
            Try
                job1Price = CDbl(txtJobPrice1.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Job Price")
                txtJobPrice1.Text = "0.00"
                txtJobPrice1.Focus()
            End Try
        End If

        If txtJobDescription2.Text = "" Then
            txtJobPrice2.Text = "0.00"
            job2Price = 0.0
        Else
            Try
                job2Price = CDbl(txtJobPrice2.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Job Price")
                txtJobPrice2.Text = "0.00"
                txtJobPrice2.Focus()
            End Try
        End If

        If txtJobDescription3.Text = "" Then
            txtJobPrice3.Text = "0.00"
            job3Price = 0.0
        Else
            Try
                job3Price = CDbl(txtJobPrice3.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Job Price")
                txtJobPrice3.Text = "0.00"
                txtJobPrice3.Focus()
            End Try
        End If

        If txtJobDescription4.Text = "" Then
            txtJobPrice4.Text = "0.00"
            job4Price = 0.0
        Else
            Try
                job4Price = CDbl(txtJobPrice4.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Job Price")
                txtJobPrice4.Text = "0.00"
                txtJobPrice4.Focus()
            End Try
        End If

        If txtJobDescription5.Text = "" Then
            txtJobPrice5.Text = "0.00"
            job5Price = 0.0
        Else
            Try
                job5Price = CDbl(txtJobPrice5.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Job Price")
                txtJobPrice5.Text = "0.00"
                txtJobPrice5.Focus()
            End Try
        End If

        SubTotalPart1 = UnitPricePart1 * QuantityPart1
        SubTotalPart2 = UnitPricePart2 * QuantityPart2
        SubTotalPart3 = UnitPricePart3 * QuantityPart3
        SubTotalPart4 = UnitPricePart4 * QuantityPart4
        SubTotalPart5 = UnitPricePart5 * QuantityPart5

        txtSubTotal1.Text = FormatNumber(SubTotalPart1)
        txtSubTotal2.Text = FormatNumber(SubTotalPart2)
        txtSubTotal3.Text = FormatNumber(SubTotalPart3)
        txtSubTotal4.Text = FormatNumber(SubTotalPart4)
        txtSubTotal5.Text = FormatNumber(SubTotalPart5)

        TotalParts = SubTotalPart1 + SubTotalPart2 + _
                     SubTotalPart3 + SubTotalPart4 + SubTotalPart5

        TotalLabor = Job1Price + Job2Price + Job3Price + _
                        Job4Price + Job5Price

        Try
            TaxRate = CDbl(txtTaxRate.Text)
        Catch Exc As FormatException
            MsgBox("Invalid Tax Rate")
            txtTaxRate.Text = "7.75"
            txtTaxRate.Focus()
        End Try

        Dim totalPartsAndLabor As Double = totalParts + totalLabor
        TaxAmount = totalPartsAndLabor * TaxRate / 100
        TotalOrder = totalPartsAndLabor + TaxAmount

        txtTotalParts.Text = FormatNumber(TotalParts)
        txtTotalLabor.Text = FormatNumber(TotalLabor)
        txtTaxAmount.Text = FormatNumber(TaxAmount)
        txtTotalOrder.Text = FormatNumber(TotalOrder)
    End Sub
End Class

In the Class Name combo box, select mnuFileNew

In the Method Name combo box, select Click and implement the event as follows:

Private Sub mnuFileNew_Click(ByVal sender As Object, _
                                 ByVal e As System.EventArgs) _
                                 Handles mnuFileNew.Click
        txtCustomerName.Text = ""
        txtAddress.Text = ""
        txtCity.Text = ""
        txtState.Text = ""
        txtZIPCode.Text = ""
        txtMake.Text = ""
        txtModel.Text = ""
        txtCarYear.Text = ""
        txtProblem.Text = ""

        txtPartName1.Text = ""
        txtUnitPrice1.Text = "0.00"
        txtQuantity1.Text = "0"
        txtSubTotal1.Text = "0.00"
        txtPartName2.Text = ""
        txtUnitPrice2.Text = "0.00"
        txtQuantity2.Text = "0"
        txtSubTotal2.Text = "0.00"
        txtPartName3.Text = ""
        txtUnitPrice3.Text = "0.00"
        txtQuantity3.Text = "0"
        txtSubTotal3.Text = "0.00"
        txtPartName4.Text = ""
        txtUnitPrice4.Text = "0.00"
        txtQuantity4.Text = "0"
        txtSubTotal4.Text = "0.00"
        txtPartName5.Text = ""
        txtUnitPrice5.Text = "0.00"
        txtQuantity5.Text = "0"
        txtSubTotal5.Text = "0.00"

        txtJobDescription1.Text = ""
        txtJobPrice1.Text = "0.00"
        txtJobDescription2.Text = ""
        txtJobPrice2.Text = "0.00"
        txtJobDescription3.Text = ""
        txtJobPrice3.Text = "0.00"
        txtJobDescription4.Text = ""
        txtJobPrice4.Text = "0.00"
        txtJobDescription5.Text = ""
        txtJobPrice5.Text = "0.00"

        txtTotalParts.Text = "0.00"
        txtTotalLabor.Text = "0.00"
        txtTaxRate.Text = "7.75"
        txtTaxAmount.Text = "0.00"
        txtTotalOrder.Text = "0.00"

        txtRecommendations.Text = ""
        txtCustomerName.Focus()
End Sub

Under the above End Sub line, create the following common eventand click the first text box under Unit Price
In the Properties window, click the Events button and double-click Leave

Call the Calculate() method as follows:

Private Sub ControlsLeave(ByVal sender As Object, _
                              ByVal e As EventArgs) _
                              Handles txtUnitPrice1.Leave, _
                                      txtUnitPrice2.Leave, _
                                      txtUnitPrice3.Leave, _
                                      txtUnitPrice4.Leave, _
                                      txtUnitPrice5.Leave, _
                                      txtQuantity1.Leave, _
                                      txtQuantity2.Leave, _
                                      txtQuantity3.Leave, _
                                      txtQuantity4.Leave, _
                                      txtQuantity5.Leave, _
                                      txtJobPrice1.Leave, _
                                      txtJobPrice2.Leave, _
                                      txtJobPrice3.Leave, _
                                      txtJobPrice4.Leave, _
                                      txtJobPrice5.Leave, _
                                      txtTaxRate.Leave
        Calculate()
End Sub

Return to the form
From the Printing section of the Toolbox, click the PrintDocument button and click the form
While the print document control is still selected, in the Properties window, change its name to docPrint
Right-click the form and click View Code
In the Class name combo box, select docPrint

In the Method Name combo box, select PrintPage and implement the event as follows:

Private Sub docPrint_PrintPage(ByVal sender As Object, _
               ByVal e As System.Drawing.Printing.PrintPageEventArgs) _
                                   Handles docPrint.PrintPage
    e.Graphics.DrawLine(New Pen(Color.Black, 2), 60, 90, 680, 90)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), 60, 93, 680, 93)

    Dim strDisplay As String = "College Park Auto Repair"
    Dim fntString As System.Drawing.Font = _
		New Font("Times New Roman", 28, _
    		         FontStyle.Bold)
    e.Graphics.DrawString(strDisplay, fntString, _
                    Brushes.Black, 160, 100)

    strDisplay = "Customer Car Repair Order"
    fntString = New System.Drawing.Font("Times New Roman", 18, _
                    FontStyle.Bold)
    e.Graphics.DrawString(strDisplay, fntString, _
                Brushes.Black, 220, 150)

    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			60, 184, 680, 184)
    e.Graphics.DrawLine(New Pen(Color.Black, 2), _
			60, 187, 680, 187)

    fntString = New System.Drawing.Font("Times New Roman", _
					12, FontStyle.Bold)
    e.Graphics.DrawString("Order Identification", fntString, _
    		          Brushes.Black, 80, 200)

    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 250, 640, 250)

    fntString = New System.Drawing.Font("Times New Roman", _
					10, FontStyle.Bold)
    e.Graphics.DrawString("Customer Name:", fntString, _
    			  Brushes.Black, 100, 260)
    fntString = New System.Drawing.Font("Times New Roman", 10, _
    			                FontStyle.Regular)
    e.Graphics.DrawString(txtCustomerName.Text, fntString, _
    	                  Brushes.Black, 260, 260)

    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 280, 640, 280)

    fntString = New Font("Times New Roman", 10, FontStyle.Bold)
    e.Graphics.DrawString("Address:", fntString, _
		            Brushes.Black, 100, 290)
    fntString = New Font("Times New Roman", _
 			 10, FontStyle.Regular)
    e.Graphics.DrawString(txtAddress.Text, fntString, _
    		          Brushes.Black, 260, 290)

    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 310, 640, 310)

    fntString = New Font("Times New Roman", _
			 10, FontStyle.Regular)
    Dim strAddress As String = txtCity.Text.ToString()& ", " & _
    			    txtState.Text(+" " & txtZIPCode.Text)
    e.Graphics.DrawString(strAddress, fntString, _
 			  Brushes.Black, 260, 320)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 340, 640, 340)

    fntString = New Font("Times New Roman", 10, FontStyle.Bold)
    e.Graphics.DrawString("Car:", fntString, _
			  Brushes.Black, 100, 350)
    fntString = New Font("Times New Roman", _
			 10, FontStyle.Regular)
    Dim strCar As String = txtMake.Text & ", " & txtModel.Text & _
                            ", " & txtCarYear.Text
    e.Graphics.DrawString(strCar, fntString, _
  			  Brushes.Black, 260, 350)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 370, 640, 370)

    fntString = New Font("Times New Roman", 10, FontStyle.Bold)
    e.Graphics.DrawString("Problem Description:", fntString, _
                Brushes.Black, 100, 380)
    fntString = New Font("Times New Roman", _
			 10, FontStyle.Regular)
    e.Graphics.DrawString(txtProblem.Text, fntString, _
                              Brushes.Black, _
                              New RectangleF(260, 380, 420, 380))
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 400, 640, 400)

    fntString = New System.Drawing.Font("Times New Roman", _
					12, FontStyle.Bold)
    e.Graphics.DrawString("Parts Used", fntString, _
    		            Brushes.Black, 80, 430)

    e.Graphics.DrawLine(New Pen(Color.Black, 2), _
			80, 450, 680, 450)

    e.Graphics.DrawString("Parts Name", fntString, _
		            Brushes.Black, 100, 460)
    e.Graphics.DrawString("Unit Price", fntString, _
    		          Brushes.Black, 420, 460)
    e.Graphics.DrawString("Qty", fntString, _
    		          Brushes.Black, 520, 460)
    e.Graphics.DrawString("Sub-Total", fntString, _
    		          Brushes.Black, 562, 460)

    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 480, 640, 480)

    fntString = New Font("Times New Roman", 10, _
			 FontStyle.Regular)
    Dim fmtString As StringFormat = New StringFormat
    fmtString.Alignment = StringAlignment.Far

    e.Graphics.DrawString(txtPartName1.Text, fntString, _
    		          Brushes.Black, 100, 490)
    e.Graphics.DrawString(txtUnitPrice1.Text, fntString, _
    		        Brushes.Black, 480, 490, fmtString)
    e.Graphics.DrawString(txtQuantity1.Text, fntString, _
    		        Brushes.Black, 540, 490, fmtString)
    e.Graphics.DrawString(txtSubTotal1.Text, fntString, _
    		        Brushes.Black, 630, 490, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    		            100, 510, 640, 510)

    e.Graphics.DrawString(txtPartName2.Text, fntString, _
            Brushes.Black, 100, 520)
    e.Graphics.DrawString(txtUnitPrice2.Text, fntString, _
            Brushes.Black, 480, 520, fmtString)
    e.Graphics.DrawString(txtQuantity2.Text, fntString, _
            Brushes.Black, 540, 520, fmtString)
    e.Graphics.DrawString(txtSubTotal2.Text, fntString, _
            Brushes.Black, 630, 520, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 540, 640, 540)

    e.Graphics.DrawString(txtPartName3.Text, fntString, _
            Brushes.Black, 100, 550)
    e.Graphics.DrawString(txtUnitPrice3.Text, fntString, _
            Brushes.Black, 480, 550, fmtString)
    e.Graphics.DrawString(txtQuantity3.Text, fntString, _
            Brushes.Black, 540, 550, fmtString)
    e.Graphics.DrawString(txtSubTotal3.Text, fntString, _
            Brushes.Black, 630, 550, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
                100, 570, 640, 570)

    e.Graphics.DrawString(txtPartName4.Text, fntString, _
            Brushes.Black, 100, 580)
    e.Graphics.DrawString(txtUnitPrice4.Text, fntString, _
            Brushes.Black, 480, 580, fmtString)
    e.Graphics.DrawString(txtQuantity4.Text, fntString, _
            Brushes.Black, 540, 580, fmtString)
    e.Graphics.DrawString(txtSubTotal4.Text, fntString, _
            Brushes.Black, 630, 580, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 600, 640, 600)

    e.Graphics.DrawString(txtPartName5.Text, fntString, _
            Brushes.Black, 100, 610)
    e.Graphics.DrawString(txtUnitPrice5.Text, fntString, _
            Brushes.Black, 480, 610, fmtString)
    e.Graphics.DrawString(txtQuantity5.Text, fntString, _
            Brushes.Black, 540, 610, fmtString)
    e.Graphics.DrawString(txtSubTotal5.Text, fntString, _
            Brushes.Black, 630, 610, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 630, 640, 630)

    fntString = New Font("Times New Roman", _
			12, FontStyle.Bold)
    e.Graphics.DrawString("Jobs Performed", fntString, _
            Brushes.Black, 80, 650)
    e.Graphics.DrawLine(New Pen(Color.Black, 2), _
			80, 670, 680, 670)

    e.Graphics.DrawString("Job Name", fntString, _
			Brushes.Black, 100, 680)
    e.Graphics.DrawString("Price", fntString, _
			Brushes.Black, 562, 680)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 700, 640, 700)

    fntString = New Font("Times New Roman", 10, _
			FontStyle.Regular)

    e.Graphics.DrawString(txtJobDescription1.Text, fntString, _
            Brushes.Black, 100, 710)
    e.Graphics.DrawString(txtJobPrice1.Text, fntString, _
            Brushes.Black, 600, 710, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 730, 640, 730)

    e.Graphics.DrawString(txtJobDescription2.Text, fntString, _
            Brushes.Black, 100, 740)
    e.Graphics.DrawString(txtJobPrice2.Text, fntString, _
            Brushes.Black, 600, 740, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 760, 640, 760)

    e.Graphics.DrawString(txtJobDescription3.Text, fntString, _
            Brushes.Black, 100, 770)
    e.Graphics.DrawString(txtJobPrice3.Text, fntString, _
                Brushes.Black, 600, 770, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 790, 640, 790)

    e.Graphics.DrawString(txtJobDescription4.Text, _
			fntString, Brushes.Black, 100, 800)
    e.Graphics.DrawString(txtJobPrice4.Text, fntString, _
                Brushes.Black, 600, 800, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 820, 640, 820)

    e.Graphics.DrawString(txtJobDescription5.Text, _
			fntString, Brushes.Black, 100, 830)
    e.Graphics.DrawString(txtJobPrice5.Text, fntString, _
                Brushes.Black, 600, 830, fmtString)
    e.Graphics.DrawLine(New Pen(Color.Black, 1), _
			100, 850, 640, 850)

    fntString = New System.Drawing.Font("Times New Roman", _
  			12, FontStyle.Bold)
    e.Graphics.DrawString("Order Summary", fntString, _
                Brushes.Black, 80, 870)
    e.Graphics.DrawLine(New Pen(Color.Black, 2), _
			80, 890, 680, 890)

    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Bold)
    e.Graphics.DrawString("Total Parts:", fntString, _
                Brushes.Black, 500, 900)
    fntString = New System.Drawing.Font("Times New Roman", _
 			10, FontStyle.Regular)
    e.Graphics.DrawString(txtTotalParts.Text, fntString, _
                Brushes.Black, 640, 900, fmtString)

    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Bold)
    e.Graphics.DrawString("Total Labor:", fntString, _
                Brushes.Black, 500, 920)
    fntString = New System.Drawing.Font("Times New Roman", _
 			10, FontStyle.Regular)
    e.Graphics.DrawString(txtTotalLabor.Text, fntString, _
                Brushes.Black, 640, 920, fmtString)

    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Bold)
    e.Graphics.DrawString("Tax Rate:", fntString, _
                Brushes.Black, 500, 940)
    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Regular)
    e.Graphics.DrawString(txtTaxRate.Text, fntString, _
                Brushes.Black, 640, 940, fmtString)

    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Bold)
    e.Graphics.DrawString("Tax Amount:", fntString, _
                Brushes.Black, 500, 960)
    fntString = New System.Drawing.Font("Times New Roman", _
 			10, FontStyle.Regular)
    e.Graphics.DrawString(txtTaxAmount.Text, fntString, _
                Brushes.Black, 640, 960, fmtString)

    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Bold)
    e.Graphics.DrawString("Repair Total:", fntString, _
                Brushes.Black, 500, 980)
    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Regular)
    e.Graphics.DrawString(txtTotalOrder.Text, fntString, _
                Brushes.Black, 640, 980, fmtString)

    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Bold)
    e.Graphics.DrawString("Recommendations:", fntString, _
            Brushes.Black, 100, 900)
    fntString = New System.Drawing.Font("Times New Roman", _
			10, FontStyle.Regular)
    e.Graphics.DrawString(txtRecommendations.Text, fntString, _
                Brushes.Black, New RectangleF(100, 920, 350, 280))
End Sub

Return to the form
From the Printing section of the Toolbox, click the PrintDialog button and click the form
While the print control is still selected, in the Properties window, change its Name to dlgPrint
Click Document and select docPrint
Right-click the form and click View Code
In the Class Name combo box, select mnuFilePrint

In the Method Name combo box, select Click and implement the event as follows:

Private Sub mnuFilePrint_Click(ByVal sender As Object, _
                                   ByVal e As System.EventArgs) _
                                   Handles mnuFilePrint.Click
        If dlgPrint.ShowDialog() = DialogResult.OK Then
            docPrint.Print()
        End If
End Sub

Return to the form
From the Printing section of the Toolbox, click PrintPreviewDialog and click the form
In the Properties window, change its (Name) to dlgPrintPreview
Still in the Properties windows, set its Document property to docPrint
Right-click the form and click View Code
In the Class Name combo box, select mnuFilePrintPreview

In the Method Name combo box, select Click and implement the event as follows:

Private Sub mnuFilePrintPreview_Click(ByVal sender As Object, _
                                          ByVal e As System.EventArgs) _
                                          Handles mnuFilePrintPreview.Click
        dlgPrintPreview.ShowDialog()
End Sub

Save the file
Return to the form

The XML Text Writer Fundamentals

Besides the XmlDocument and the derived classes of XmlNode, the .NET Framework provides the XmlTextWriter class, which is derived from XmlWriter. The XmlTextWriter class works in a top-down approach to create, or deal with, the contents of an XML file. This class writes an XML node and moves down without referring back:

This means that, once you have created a node using the XmlTextWriter, you have no way of referring back to it.

To use an XmlTextWriter object, first declare a variable of the type of this class and initialize it using one of its three constructors.

If you had already created a Stream-based object such as declaring a variable of type FileStream but you did not define an encoding scheme, you can pass the Stream-based object to an XmlTextWriter but you must take this time to specify the encoding scheme. To support this concept, the XmlTextWriter provides a constructor with the following syntax:

Public Sub New(w As Stream, encoding As Encoding)

The first argument of this constructor can be a Stream-based variable. The second argument specifies the encoding scheme that would be applied. The default is UTF-8. Based on this, if you want to use the UTF-8 encoding scheme, you can pass it or pass the argument as 0. If you want to use another encoding scheme, pass it to the constructor.

To work from scratch, that is, to initiate a file with manually-created nodes, you can pass the desired name of the file to the XmlTextWriter constructor using the following syntax:

Public Sub New(filename As String, encoding As Encoding)

In this case, you must provide the name of, or path to, the file, whose content you are creating, as the first argument. You must pass the desired encoding scheme as the second argument. Here is an example:

Imports System.Xml
Imports System.IO
Imports System.Text

Public Class Exercise

    Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)
    End Sub
End Class

Eventually, when you have finished using the XmlTextWriter object, you must free the memory it was using by calling the XmlTextWriter.Flush() method. To release the resources that the object was using, call the XmlTextWriter.Close() method. Here is an example:

Imports System.Xml
Imports System.IO
Imports System.Text

Public Class Exercise

    Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.Flush()
        Writer.Close()
    End Sub
End Class

Creating the XML Declaration

Declaring an XmlTextWriter variable allows you to indicate that you intend to create a new XML file. With the variable ready, you can start writing the file's content. As mentioned in previous lessons, an XML file starts at the top with an XML declaration. To create this declaration, you can call the XmlTextWriter.WriteStartDocument() method. This method is overloaded with two versions. The syntax of one of them is:

Public Overrides Sub WriteStartDocument

This method creates a declaration, sets the XML version to 1.0, and includes the encoding scheme you specified in the constructor. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.Flush()
        Writer.Close()
End Sub

To end an XML file, you must close its declaration. This is done by calling the XmlTextWriter.WriteEndDocument() method. Its syntax is:

Public Overrides Sub WriteEndDocument

This method indicates that the XML file has ended and allows the compiler to stop reading it down. This would be done as follows:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

Creating the Root Element

Between the XML declaration and the end of the file, that is, between the call to XmlTextWriter.WriteStartDocument() and the call to XmlTextWriter.WriteEndDocument() methods, you can create the necessary nodes of the file. As reviewed in previous lessons, the most regular node of an XML file is the element. To create an element, the XmlTextWriter class provides the WriteStartElement() method that is overloaded with various versions. One of the versions of this method, and that is inherited from the XmlWriter class, uses the following syntax:

Public Sub WriteStartElement(localName As String)

This method takes as argument the name of the element that will be created. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteStartElement("students")

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

As you may know from XML, every element must be closed. To close an XML element, call the XmlTextWriter.WriteEndElement() method. Its syntax is:

Public Overrides Sub WriteEndElement

When calling this method, always make sure that you know the element it is closing, which must correspond to an appropriate previous call to a WriteStartElement() method. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteStartElement("students")
        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

This would produce:

As you can see from the result, a single or the first call to the WriteStartElement() method creates the root element that is required for every XML file. This means that, after this (first) call but before its corresponding WriteEndElement() call, you can create the necessary nodes that you want to include as part of the file.

Creating the Child Elements of the Root

To help you create child elements of the root node, you can keep calling the XmlTextWriter.WriteStartElement() method as necessary and appropriately closing it. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
    Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

    Writer.WriteStartDocument()

    Writer.WriteStartElement("students")

        Writer.WriteStartElement("student")
        Writer.WriteEndElement()

        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

If you simply call this method as done above, the element would be empty. Based on this, the above code would produce:

If you want the element to have a value, call the XmlTextWriter.WriteString() method. Its syntax is:

Public Overrides Sub WriteString(text As String)

This method must immediately follow the call to WriteStartElement() that creates a new element. It takes as argument the value for the immediately previously defined element. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteStartElement("students")

        Writer.WriteStartElement("student")
        Writer.WriteString("Raymond Sanson")
        Writer.WriteEndElement()

        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

This would produce:

If you call the XmlTextWriter.WriteStartElement() method and you want the element to have a value, remember to call the XmlTextWriter.WriteString() method, and then call the XmlTextWriter.WriteEndElement() method. An alternative is to call the XmlWriter.WriteElementString() method that comes in two versions. The syntax of one of these versions is:

Public Sub WriteElementString(localName As String, _
			      value As String)

The first argument to this method is the name of the element that will be created. The second argument is the value of the element. This method creates and closes its element. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteStartElement("students")

        Writer.WriteStartElement("student")
        Writer.WriteString("Raymond Sanson")
        Writer.WriteEndElement()

        Writer.WriteElementString("student", "Brigitte Arano")

        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

This would produce:

In the same way, you can create the necessary elements and their child elements as necessary. Be careful to appropriately start an element and remember to close it if necessary. Here are examples:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = New XmlTextWriter("students.xml", _
                                                    Encoding.UTF8)

        Writer.WriteStartDocument()

        ' Create the root element named students
        Writer.WriteStartElement("students")

        ' Start a child element named student
        Writer.WriteStartElement("student")

        ' Create a number for the student
        Writer.WriteStartElement("studentnumber")
        Writer.WriteString("740597")
        Writer.WriteEndElement()

        ' Create a name for the student
        Writer.WriteStartElement("fullname")
        Writer.WriteString("Christie Aronson")
        Writer.WriteEndElement()

        ' Create a date of birth for the student
        Writer.WriteStartElement("dateofbirth")
        Writer.WriteString("02/16/1988")
        Writer.WriteEndElement()

        ' Create a Format child element to the Video element
        Writer.WriteStartElement("Gender")
        Writer.WriteString("Female")
        Writer.WriteEndElement()

        ' Close the student node
        Writer.WriteEndElement()

        ' Start a new student element
        Writer.WriteStartElement("student")

        ' Create the child elements of the new student element
        Writer.WriteElementString("studentnumber", "249575")
        Writer.WriteElementString("fullname", "Julius Raymonds")
        Writer.WriteElementString("dateofbirth", "12/07/1992")
        Writer.WriteElementString("Gender", "Male")
        ' The current student node
        Writer.WriteEndElement()

        ' Close the root element
        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

This would produce:

Practical Learning: Creating the Elements of an XML File

From the Dialogs section of the Toolbox, click SaveFileDialog and click the form
Change its properties as follows:
Title: Save Current Repair Order
DefaultExt: xml
Filter: Repair Orders (*.xml)|*.xml|All Files|
Name: dlgSave
Right-click the form and click View Code
In the Class Name combo box, select mnuFileSave

In the Method Name combo box, select Click and implement the event as follows:

Private Sub mnuFileSave_Click(ByVal sender As Object, _
                              ByVal e As System.EventArgs) _
                              Handles mnuFileSave.Click
    ' Just in case, calculate the order now
    Calculate()
    ' This number will be used to incrementally
    ' create the files by their names
    Dim iFilename As Integer
    Dim Filename As String
    ' If this directory doesn't exist, create it
    ' Also, get a reference to this directory for later use
    Dim FolderName As String = "C:\College Park Auto Repair"
    Dim Folder As DirectoryInfo = Directory.CreateDirectory(FolderName)

    ' Get the list of files, if any, from the above folder
    Dim ListOfFiles() As FileInfo = Folder.GetFiles("*.xml")

    ' If there is no XML file in the directory,
    ' then get ready to create the first file
    If ListOfFiles.Length = 0 Then
        ' Create the name of the (initial) file
        iFilename = 1000
    Else ' If there was at least one file in the directory
        ' Get a reference to the last file
        Dim fleLast As FileInfo = ListOfFiles(ListOfFiles.Length - 1)
        ' Get the name of the last file without its extension
        Dim fwe As String = Path.GetFileNameWithoutExtension(fleLast.FullName)
        ' Get the name of the file
        iFilename = CInt(fwe)
    End If

    Filename = FolderName& """" & cstr(iFilename + 1)& ".xml"

    ' Get ready to display it in the Save dialog box
    dlgSave.FileName = Filename

    ' Find out if the user clicked OK after displaying the Save dialog box
    If dlgSave.ShowDialog() = DialogResult.OK Then
        Dim wtrRepairOrder As XmlTextWriter = New XmlTextWriter(Filename, _
                    Encoding.UTF8)

        ' Create the contents of the XML file
        ' Notice that we are not making an attempt to check the values
        wtrRepairOrder.WriteStartDocument()

        wtrRepairOrder.WriteStartElement("RepairOrders")
        wtrRepairOrder.WriteStartElement("Invoice")

        wtrRepairOrder.WriteElementString("CustomerName", txtCustomerName.Text)
            wtrRepairOrder.WriteElementString("Addres", txtAddress.Text)
            wtrRepairOrder.WriteElementString("City", txtCity.Text)
            wtrRepairOrder.WriteElementString("State", txtState.Text)
            wtrRepairOrder.WriteElementString("ZIPCode", txtZIPCode.Text)
            wtrRepairOrder.WriteElementString("Make", txtMake.Text)
            wtrRepairOrder.WriteElementString("Model", txtModel.Text)
            wtrRepairOrder.WriteElementString("CarYear", txtCarYear.Text)
        wtrRepairOrder.WriteElementString("ProbDescription", txtProblem.Text)
            wtrRepairOrder.WriteElementString("PartName1", txtPartName1.Text)
            wtrRepairOrder.WriteElementString("UnitPrice1", txtUnitPrice1.Text)
            wtrRepairOrder.WriteElementString("Quantity1", txtQuantity1.Text)
            wtrRepairOrder.WriteElementString("SubTotal1", txtSubTotal1.Text)
            wtrRepairOrder.WriteElementString("PartName2", txtPartName2.Text)
            wtrRepairOrder.WriteElementString("UnitPrice2", txtUnitPrice2.Text)
            wtrRepairOrder.WriteElementString("Quantity2", txtQuantity2.Text)
            wtrRepairOrder.WriteElementString("SubTotal2", txtSubTotal2.Text)
            wtrRepairOrder.WriteElementString("PartName3", txtPartName3.Text)
            wtrRepairOrder.WriteElementString("UnitPrice3", txtUnitPrice3.Text)
            wtrRepairOrder.WriteElementString("Quantity3", txtQuantity3.Text)
            wtrRepairOrder.WriteElementString("SubTotal3", txtSubTotal3.Text)
            wtrRepairOrder.WriteElementString("PartName4", txtPartName4.Text)
            wtrRepairOrder.WriteElementString("UnitPrice4", txtUnitPrice4.Text)
            wtrRepairOrder.WriteElementString("Quantity4", txtQuantity4.Text)
            wtrRepairOrder.WriteElementString("SubTotal4", txtSubTotal4.Text)
            wtrRepairOrder.WriteElementString("PartName5", txtPartName5.Text)
            wtrRepairOrder.WriteElementString("UnitPrice5", txtUnitPrice5.Text)
            wtrRepairOrder.WriteElementString("Quantity5", txtQuantity5.Text)
            wtrRepairOrder.WriteElementString("SubTotal5", txtSubTotal5.Text)
        wtrRepairOrder.WriteElementString("JobDescription1", _
					  txtJobDescription1.Text)
            wtrRepairOrder.WriteElementString("JobPrice1", txtJobPrice1.Text)
        wtrRepairOrder.WriteElementString("JobDescription2", _
					  txtJobDescription2.Text)
            wtrRepairOrder.WriteElementString("JobPrice2", txtJobPrice2.Text)
        wtrRepairOrder.WriteElementString("JobDescription3", _
					  txtJobDescription3.Text)
            wtrRepairOrder.WriteElementString("JobPrice3", txtJobPrice3.Text)
        wtrRepairOrder.WriteElementString("JobDescription4", _
					  txtJobDescription4.Text)
            wtrRepairOrder.WriteElementString("JobPrice4", txtJobPrice4.Text)
        wtrRepairOrder.WriteElementString("JobDescription5", _
					  txtJobDescription5.Text)
            wtrRepairOrder.WriteElementString("JobPrice5", txtJobPrice5.Text)
            wtrRepairOrder.WriteElementString("TotalPart", txtTotalParts.Text)
            wtrRepairOrder.WriteElementString("TotalLabor", txtTotalLabor.Text)
            wtrRepairOrder.WriteElementString("TaxRate", txtTaxRate.Text)
            wtrRepairOrder.WriteElementString("TaxAmount", txtTaxAmount.Text)
            wtrRepairOrder.WriteElementString("TotalOrder", txtTotalOrder.Text)
        wtrRepairOrder.WriteElementString("Recommendation", _
					  txtRecommendations.Text)

            wtrRepairOrder.WriteEndElement()
            wtrRepairOrder.WriteEndElement()

            wtrRepairOrder.WriteEndDocument()

            wtrRepairOrder.Flush()
            wtrRepairOrder.Close()
        End If
End Sub

Execute the application to test it
Create a new record and click Calculate Order:
Click File -> Save and OK to Save the file
Click File -> New Repair Order
Create another repair order:
Save it
Close the form and return to your programming environment

Saving a File As XML

If you are creating a text-intensive document and you want to save it as an XML file, for example if you have declared a variable of type TextWriter-derived class (such as StringWriter or StreamWriter), you can use that file to initialize the XmlTextWriter variable. To support TextWriter documents, the XmlTextWriter class is equipped with a constructor with the following syntax:

Public Sub New(w As TextWriter)

This constructor expects as argument a TextWriter-based object. This means that you should have defined the TextWriter object prior to passing it to this constructor. This also implies that the TextWriter was used to specify the encoding scheme that would be used. Here is an example:

Private Sub btnCreate_Click(ByVal sender As Object, _
                                ByVal e As System.EventArgs) _
                                Handles btnCreate.Click
    Dim Filename As String = "students.xml"
    Dim fleStream As FileStream = _
	New FileStream("students.xml", FileMode.Create, _
                       FileAccess.Write, FileShare.None)
    Dim stmWriter As StreamWriter = New StreamWriter(fleStream)
    Dim txtWriter As XmlTextWriter = New XmlTextWriter(stmWriter)

    stmWriter.Flush()
    stmWriter.Close()
End Sub

To actually write the contents of the document, you can create each paragraph by calling the XmlTextWriter.WriteStartElement() method the same way we did earlier. Here is an example:

Private Sub btnCreate_Click(ByVal sender As Object, _
                                ByVal e As System.EventArgs) _
                                Handles btnCreate.Click
        Dim Filename As String = "students.xml"
        Dim fleStream As FileStream = New FileStream("students.xml", _
                      FileMode.Create, _
                      FileAccess.Write, _
                      FileShare.None)
        Dim stmWriter As StreamWriter = New StreamWriter(fleStream)
        Dim txtWriter As XmlTextWriter = New XmlTextWriter(stmWriter)

        txtWriter.WriteStartDocument()
        txtWriter.WriteStartElement("ToAllEmployees")

        For i As Integer = 0 To txtEditor.Lines.Length - 1
            txtWriter.WriteStartElement("Notice")
            txtWriter.WriteString(txtEditor.Lines(i))
            txtWriter.WriteEndElement()
        Next

        txtWriter.WriteEndDocument()

        stmWriter.Flush()
        stmWriter.Close()
End Sub

Reading From an XML File

Introduction

Once an XML file exists, you can read it to retrieve the values of its nodes. To support opening an XML file and reading its contents, the .NET Framework provides the XmlTextReader class that is derived from the XmlReader class. The XmlTextReader class is equipped with all the necessary properties and methods to explore the contents of an XML file.

Like XmlTextWriter, the XmlTextReader class reads a file from top to bottom without going back up once it has passed a node:

This means that, when using the XmlTextReader class to read an XML file, once you have read a node and moved down the file, you cannot refer back to the previous node and you cannot access a previous node.

Using and XML Text Reader

To use an XML text reader, declare a variable of type XmlTextReader and initialize it with one of its constructors. The class is equipped with 14 constructors. If you want to open a file whose name or path you know, use the following constructor:

Public Sub New(url As String)

This constructor takes as argument the name of, or path to, an XML file. If the file is found, it would be opened. If the file does not exist or there is an error in the string that specifies its path, the compiler would throw an XmlException exception.

Reading Nodes

After declaring an XmlTextReader variable, you can start reading the content of the file. To support this, you can call the XmlTextReader.Read() method. Its syntax is:

Public Overrides Function Read As Boolean

As mentioned previously, the file is read from top to bottom. Based on this, when you call the Read() method, it reads the first node, moves to the next, and so on until it reaches the end of the file. While reading the file, every time this method reaches a node, you can find out what type of node it is by checking the XmlTextReader.NodeType property. This can help you take a specific action if the reached node meets a certain criterion.

As reviewed in our introductions to XML, each node has a name and possibly a value. You can find out the name of a node by checking the XmlTextReader.Name property. To know the value of a node, retrieve its XmlTextReader.Value property.

Practical Learning: Reading the Elements of an XML File

Display the form.
From the Dialogs section of the Toolbox, click OpenFileDialog and click the form
Change its properties as follows:
Title: Open Existing Repair Order
DefaultExt: xml
Filter: Repair Orders (*.xml)|*.xml|All Files|
Name: dlgOpen
Right-click the form and click View Code
In the Class Name combo box, select mnuFileOpen

In the Method Name combo box, select Click and implement the event as follows:

Private Sub mnuFileOpen_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles mnuFileOpen.Click
    Dim rdrRepairOrder As XmlTextReader = Nothing

    Try
        If dlgOpen.ShowDialog() = DialogResult.OK Then
            rdrRepairOrder = New XmlTextReader(dlgOpen.FileName)

            ' Scan the XML file
            Do
                ' every time you find an element, find out what type it is
                ' If you find text, put it in the combo box' list
                If (XmlNodeType.Element <> 0) And _
                   (rdrRepairOrder.Name = "CustomerName") Then
                    txtCustomerName.Text = _
                    rdrRepairOrder.ReadElementString("CustomerName")
                    txtAddress.Text = rdrRepairOrder.ReadElementString("Addres")
                    txtCity.Text = rdrRepairOrder.ReadElementString("City")
                    txtState.Text = rdrRepairOrder.ReadElementString("State")
                    txtZIPCode.Text = rdrRepairOrder.ReadElementString("ZIPCode")
                    txtMake.Text = rdrRepairOrder.ReadElementString("Make")
                    txtModel.Text = rdrRepairOrder.ReadElementString("Model")
                    txtCarYear.Text = rdrRepairOrder.ReadElementString("CarYear")
                    txtProblem.Text = _
                    rdrRepairOrder.ReadElementString("ProbDescription")
                    txtPartName1.Text = rdrRepairOrder.ReadElementString("PartName1")
                    txtUnitPrice1.Text = rdrRepairOrder.ReadElementString("UnitPrice1")
                    txtQuantity1.Text = rdrRepairOrder.ReadElementString("Quantity1")
                    txtSubTotal1.Text = rdrRepairOrder.ReadElementString("SubTotal1")
                    txtPartName2.Text = rdrRepairOrder.ReadElementString("PartName2")
                    txtUnitPrice2.Text = rdrRepairOrder.ReadElementString("UnitPrice2")
                    txtQuantity2.Text = rdrRepairOrder.ReadElementString("Quantity2")
                    txtSubTotal2.Text = rdrRepairOrder.ReadElementString("SubTotal2")
                    txtPartName3.Text = rdrRepairOrder.ReadElementString("PartName3")
                    txtUnitPrice3.Text = rdrRepairOrder.ReadElementString("UnitPrice3")
                    txtQuantity3.Text = rdrRepairOrder.ReadElementString("Quantity3")
                    txtSubTotal3.Text = rdrRepairOrder.ReadElementString("SubTotal3")
                    txtPartName4.Text = rdrRepairOrder.ReadElementString("PartName4")
                    txtUnitPrice4.Text = rdrRepairOrder.ReadElementString("UnitPrice4")
                    txtQuantity4.Text = rdrRepairOrder.ReadElementString("Quantity4")
                    txtSubTotal4.Text = rdrRepairOrder.ReadElementString("SubTotal4")
                    txtPartName5.Text = rdrRepairOrder.ReadElementString("PartName5")
                    txtUnitPrice5.Text = rdrRepairOrder.ReadElementString("UnitPrice5")
                    txtQuantity5.Text = rdrRepairOrder.ReadElementString("Quantity5")
                    txtSubTotal5.Text = rdrRepairOrder.ReadElementString("SubTotal5")
                    txtJobDescription1.Text = _
                        rdrRepairOrder.ReadElementString("JobDescription1")
                    txtJobPrice1.Text = rdrRepairOrder.ReadElementString("JobPrice1")
                    txtJobDescription2.Text = _
                        rdrRepairOrder.ReadElementString("JobDescription2")
                    txtJobPrice2.Text = rdrRepairOrder.ReadElementString("JobPrice2")
                    txtJobDescription3.Text = _
                        rdrRepairOrder.ReadElementString("JobDescription3")
                    txtJobPrice3.Text = rdrRepairOrder.ReadElementString("JobPrice3")
                    txtJobDescription4.Text = _
                        rdrRepairOrder.ReadElementString("JobDescription4")
                    txtJobPrice4.Text = rdrRepairOrder.ReadElementString("JobPrice4")
                    txtJobDescription5.Text = _
                        rdrRepairOrder.ReadElementString("JobDescription5")
                    txtJobPrice5.Text = rdrRepairOrder.ReadElementString("JobPrice5")
                    txtTotalParts.Text = rdrRepairOrder.ReadElementString("TotalPart")
                    txtTotalLabor.Text = rdrRepairOrder.ReadElementString("TotalLabor")
                    txtTaxRate.Text = rdrRepairOrder.ReadElementString("TaxRate")
                    txtTaxAmount.Text = rdrRepairOrder.ReadElementString("TaxAmount")
                    txtTotalOrder.Text = rdrRepairOrder.ReadElementString("TotalOrder")
                    txtRecommendations.Text = _
                        rdrRepairOrder.ReadElementString("Recommendation")
                End If
            Loop While rdrRepairOrder.Read()
        End If
    Catch Exc As XmlException
        MsgBox("The file name you provided is not valid")
    Finally
        rdrRepairOrder.Close()
    End Try
End Sub

Execute the application and open one the previous orders

Details on XML Reading and Writing

Indentation

Consider a valid XML file such as the following, opened in Notepad:

If you were asked to examine this file, you can see that its crowded words make it difficult to read. To include a white space when writing to the file, you can call the XmlTextWriter.WriteWhiteSpace() method. Its syntax is:

Public Overrides Sub WriteWhitespace(ws As String)

Besides white spaces, indentation consists of setting empty spaces on the left of child nodes to make the file easier to read. Based on this, indentation is not a requirement but a convenience. While the WriteWhiteSpace() method allows you to explicitly create a white space in the file, the XmlTextWriter class is equipped with the Formatting property. This property is a value of the Formatting enumeration. The Formatting enumeration has two members. The Indented value ensures that each child node would be indented from its parent.

If you manually create an XML file, whether using Notepad, Visual Studio, or another text editor, you can indent the nodes as you see fit. To let the compiler know that you want the nodes to be indented, assign the Formatting.Indented member to its Formatting property. Here is an example:

Private Sub btnCreate_Click(ByVal sender As Object, _
                                ByVal e As System.EventArgs) _
                                Handles btnCreate.Click
    Dim Filename As String = "students.xml"
    Dim fleStream As FileStream = _
	New FileStream("students.xml", FileMode.Create, _
                       FileAccess.Write, FileShare.None)
    Dim stmWriter As StreamWriter = New StreamWriter(fleStream)
    Dim txtWriter As XmlTextWriter = New XmlTextWriter(stmWriter)

    Writer.Formatting = Formatting.Indented

    stmWriter.Flush()
    stmWriter.Close()
End Sub

If you manually create an XML file, you can specify the number of empty spaces on the left of a node by pressing the Space bar a few times before typing the node. Most people use 2 or 4 characters for the indentation. If you are programmatically creating the file, to specify the number of characters that should be used during indentation, assign the desired integer to the XmlTextWriter.Indentation property. If you don't use this property, the compiler would use two characters. You can also find out the number of characters used for indentation by retrieving the value of this property.

As mentioned above, indentation consists of entering white spaces on the left of child nodes. Instead of empty spaces, if you want to use another character, assign it to the XmlTextWriter.IndentChar property.

Practical Learning: Indenting XML Nodes

In the Class Name combo box, select mnuFileSave and, to control the indentation when the file is saved, change the top section of the event as follows:

Private Sub mnuFileSave_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles mnuFileSave.Click
    . . . No Change

    ' Find out if the user clicked OK after displaying the Save dialog box
    If dlgSave.ShowDialog() = DialogResult.OK Then
        Dim wtrRepairOrder As XmlTextWriter = New XmlTextWriter(Filename, _
                    Encoding.UTF8)
        wtrRepairOrder.Formatting = Formatting.Indented
        wtrRepairOrder.Indentation = 4

        . . . No Change
    End If
End Sub

In the Class Name combo box, select mnuFileExit

In the Method Name combo box, select Click and implement the event as follows:

Private Sub mnuFileExit_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles mnuFileExit.Click
    End
End Sub

Execute the application
Create and save a few more repair orders
Close the form

Exercises

College Park Auto-Repair

Open the College Park Auto-Repair database from this lesson
Notice that if you open a repair order, change it and try to save it, the application would create a new repair order with a new receipt number.
Configure the form so that, if a repair order was previous opened then changed, if the user saves it, the current repair order would be saved, using its own receipt number instead of generating a new receipt number


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