Programming Microsoft Visual Basic .NET/Programming Microsoft Visual Basic .NET (Microsoft Press)(X08-78517)(2002).bin/setup/vbnet/21 adonet disconnected/adonetdisconnected/datasetform.vb

Text File | 2002-03-16 | 23.5 KB | 545 lines

Public Class DataSetForm
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub
    Friend WithEvents btnCreateTable As System.Windows.Forms.Button
    Friend WithEvents DataGrid1 As System.Windows.Forms.DataGrid
    Friend WithEvents btnUppercase As System.Windows.Forms.Button
    Friend WithEvents btnSelect As System.Windows.Forms.Button
    Friend WithEvents btnDataView As System.Windows.Forms.Button
    Friend WithEvents btnRelations As System.Windows.Forms.Button
    Friend WithEvents DataGrid2 As System.Windows.Forms.DataGrid
    Friend WithEvents btnConstraints As System.Windows.Forms.Button
    Friend WithEvents btnSaveXml As System.Windows.Forms.Button
    Friend WithEvents btnEvents As System.Windows.Forms.Button

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.Container

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.btnRelations = New System.Windows.Forms.Button()
        Me.btnSelect = New System.Windows.Forms.Button()
        Me.btnCreateTable = New System.Windows.Forms.Button()
        Me.DataGrid2 = New System.Windows.Forms.DataGrid()
        Me.DataGrid1 = New System.Windows.Forms.DataGrid()
        Me.btnConstraints = New System.Windows.Forms.Button()
        Me.btnUppercase = New System.Windows.Forms.Button()
        Me.btnDataView = New System.Windows.Forms.Button()
        Me.btnSaveXml = New System.Windows.Forms.Button()
        Me.btnEvents = New System.Windows.Forms.Button()
        CType(Me.DataGrid2, System.ComponentModel.ISupportInitialize).BeginInit()
        CType(Me.DataGrid1, System.ComponentModel.ISupportInitialize).BeginInit()
        Me.SuspendLayout()
        '
        'btnRelations
        '
        Me.btnRelations.Location = New System.Drawing.Point(16, 256)
        Me.btnRelations.Name = "btnRelations"
        Me.btnRelations.Size = New System.Drawing.Size(112, 40)
        Me.btnRelations.TabIndex = 0
        Me.btnRelations.Text = "Create a Relation"
        '
        'btnSelect
        '
        Me.btnSelect.Location = New System.Drawing.Point(16, 160)
        Me.btnSelect.Name = "btnSelect"
        Me.btnSelect.Size = New System.Drawing.Size(112, 40)
        Me.btnSelect.TabIndex = 0
        Me.btnSelect.Text = "Select method"
        '
        'btnCreateTable
        '
        Me.btnCreateTable.Location = New System.Drawing.Point(16, 16)
        Me.btnCreateTable.Name = "btnCreateTable"
        Me.btnCreateTable.Size = New System.Drawing.Size(112, 40)
        Me.btnCreateTable.TabIndex = 0
        Me.btnCreateTable.Text = "Create DataTables"
        '
        'DataGrid2
        '
        Me.DataGrid2.AlternatingBackColor = System.Drawing.Color.LightGray
        Me.DataGrid2.Anchor = (((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Bottom) _
                    Or System.Windows.Forms.AnchorStyles.Left) _
                    Or System.Windows.Forms.AnchorStyles.Right)
        Me.DataGrid2.BackColor = System.Drawing.Color.DarkGray
        Me.DataGrid2.CaptionBackColor = System.Drawing.Color.White
        Me.DataGrid2.CaptionFont = New System.Drawing.Font("Verdana", 10!)
        Me.DataGrid2.CaptionForeColor = System.Drawing.Color.Navy
        Me.DataGrid2.DataMember = ""
        Me.DataGrid2.ForeColor = System.Drawing.Color.Black
        Me.DataGrid2.GridLineColor = System.Drawing.Color.Black
        Me.DataGrid2.GridLineStyle = System.Windows.Forms.DataGridLineStyle.None
        Me.DataGrid2.HeaderBackColor = System.Drawing.Color.Silver
        Me.DataGrid2.HeaderForeColor = System.Drawing.Color.Black
        Me.DataGrid2.LinkColor = System.Drawing.Color.Navy
        Me.DataGrid2.Location = New System.Drawing.Point(144, 224)
        Me.DataGrid2.Name = "DataGrid2"
        Me.DataGrid2.ParentRowsBackColor = System.Drawing.Color.White
        Me.DataGrid2.ParentRowsForeColor = System.Drawing.Color.Black
        Me.DataGrid2.SelectionBackColor = System.Drawing.Color.Navy
        Me.DataGrid2.SelectionForeColor = System.Drawing.Color.White
        Me.DataGrid2.Size = New System.Drawing.Size(488, 160)
        Me.DataGrid2.TabIndex = 2
        '
        'DataGrid1
        '
        Me.DataGrid1.AlternatingBackColor = System.Drawing.Color.LightGray
        Me.DataGrid1.Anchor = (((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Bottom) _
                    Or System.Windows.Forms.AnchorStyles.Left) _
                    Or System.Windows.Forms.AnchorStyles.Right)
        Me.DataGrid1.BackColor = System.Drawing.Color.DarkGray
        Me.DataGrid1.CaptionBackColor = System.Drawing.Color.White
        Me.DataGrid1.CaptionFont = New System.Drawing.Font("Verdana", 10!)
        Me.DataGrid1.CaptionForeColor = System.Drawing.Color.Navy
        Me.DataGrid1.DataMember = ""
        Me.DataGrid1.ForeColor = System.Drawing.Color.Black
        Me.DataGrid1.GridLineColor = System.Drawing.Color.Black
        Me.DataGrid1.GridLineStyle = System.Windows.Forms.DataGridLineStyle.None
        Me.DataGrid1.HeaderBackColor = System.Drawing.Color.Silver
        Me.DataGrid1.HeaderForeColor = System.Drawing.Color.Black
        Me.DataGrid1.LinkColor = System.Drawing.Color.Navy
        Me.DataGrid1.Location = New System.Drawing.Point(144, 16)
        Me.DataGrid1.Name = "DataGrid1"
        Me.DataGrid1.ParentRowsBackColor = System.Drawing.Color.White
        Me.DataGrid1.ParentRowsForeColor = System.Drawing.Color.Black
        Me.DataGrid1.SelectionBackColor = System.Drawing.Color.Navy
        Me.DataGrid1.SelectionForeColor = System.Drawing.Color.White
        Me.DataGrid1.Size = New System.Drawing.Size(488, 200)
        Me.DataGrid1.TabIndex = 2
        '
        'btnConstraints
        '
        Me.btnConstraints.Location = New System.Drawing.Point(16, 304)
        Me.btnConstraints.Name = "btnConstraints"
        Me.btnConstraints.Size = New System.Drawing.Size(112, 40)
        Me.btnConstraints.TabIndex = 0
        Me.btnConstraints.Text = "Add constraints"
        '
        'btnUppercase
        '
        Me.btnUppercase.Location = New System.Drawing.Point(16, 64)
        Me.btnUppercase.Name = "btnUppercase"
        Me.btnUppercase.Size = New System.Drawing.Size(112, 40)
        Me.btnUppercase.TabIndex = 0
        Me.btnUppercase.Text = "Convert to UpperCase"
        '
        'btnDataView
        '
        Me.btnDataView.Location = New System.Drawing.Point(16, 208)
        Me.btnDataView.Name = "btnDataView"
        Me.btnDataView.Size = New System.Drawing.Size(112, 40)
        Me.btnDataView.TabIndex = 0
        Me.btnDataView.Text = "Create a DataView"
        '
        'btnSaveXml
        '
        Me.btnSaveXml.Location = New System.Drawing.Point(16, 352)
        Me.btnSaveXml.Name = "btnSaveXml"
        Me.btnSaveXml.Size = New System.Drawing.Size(112, 40)
        Me.btnSaveXml.TabIndex = 0
        Me.btnSaveXml.Text = "Save as Xml"
        '
        'btnEvents
        '
        Me.btnEvents.Location = New System.Drawing.Point(16, 112)
        Me.btnEvents.Name = "btnEvents"
        Me.btnEvents.Size = New System.Drawing.Size(112, 40)
        Me.btnEvents.TabIndex = 0
        Me.btnEvents.Text = "DataEvents Events"
        '
        'DataSetForm
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(7, 17)
        Me.ClientSize = New System.Drawing.Size(648, 397)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.btnEvents, Me.btnSaveXml, Me.btnConstraints, Me.DataGrid2, Me.btnRelations, Me.btnDataView, Me.btnSelect, Me.btnUppercase, Me.DataGrid1, Me.btnCreateTable})
        Me.Font = New System.Drawing.Font("Microsoft Sans Serif", 11!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Name = "DataSetForm"
        Me.Text = "Disconnected DataSet"
        CType(Me.DataGrid2, System.ComponentModel.ISupportInitialize).EndInit()
        CType(Me.DataGrid1, System.ComponentModel.ISupportInitialize).EndInit()
        Me.ResumeLayout(False)

    End Sub

#End Region

    ' This is at the form level, to be shared among all procedures.
    Dim ds As New DataSet()

    Private Sub btnCreateTable_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCreateTable.Click

        ' --- Define the Employees table ---

        ' Create a table, set its initial capacity and case sensitiveness.
        Dim dtEmp As New DataTable("Employees")
        dtEmp.MinimumCapacity = 100
        dtEmp.CaseSensitive = False

        ' Create all columns.
        ' You can create a DataColumn and then add it to the Columns collection.
        Dim dcFName As New DataColumn("FirstName", GetType(String))
        dtEmp.Columns.Add(dcFName)
        ' Or you can create an implicit DataColumn with the Columns.Add method.
        dtEmp.Columns.Add("LastName", GetType(String))
        dtEmp.Columns.Add("BirthDate", GetType(Date))

        ' When you have to set additional properties, you can use an explicit
        ' DataColumn object, or you can use a With block.
        With dtEmp.Columns.Add("HomeAddress", GetType(String))
            .MaxLength = 100
        End With
        ' (When you must set only one property you can be even more concise,
        '  even though the result isn't very readable.)
        dtEmp.Columns.Add("City", GetType(String)).MaxLength = 20

        ' Create a calculated column, by passing setting the Expression
        ' property or passing it as the 3rd argument to the Add method.
        dtEmp.Columns.Add("CompleteName", GetType(String), "FirstName + ' ' + LastName")

        ' Create an ID column.
        Dim dcEmpId As New DataColumn("EmpId", GetType(Integer))
        dcEmpId.AutoIncrement = True        ' Make it autoincrement.
        dcEmpId.AutoIncrementSeed = 1
        dcEmpId.AllowDBNull = False         ' Default is True.
        dcEmpId.Unique = True
        dtEmp.Columns.Add(dcEmpId)          ' Add to Columns collection.

        ' Make it the primary key.
        Dim pkCols() As DataColumn = {dcEmpId}
        dtEmp.PrimaryKey = pkCols
        ' (You can also use a more concise form, as follows:)
        dtEmp.PrimaryKey = New DataColumn() {dcEmpId}

        ' This is a foreign key, but we haven't created the other table yet.
        dtEmp.Columns.Add("DeptId", GetType(Integer))

        ' Add the DataTable to the DataSet.
        ds.Tables.Add(dtEmp)

        ' Show the result in the DataGrid.
        DataGrid2.DataSource = dtEmp

        ' -- fill the Employees table

        ' Create a new row with same schema.
        Dim dr As DataRow = dtEmp.NewRow()
        ' Set all the columns.
        dr("FirstName") = "Joe"
        dr("LastName") = "Doe"
        dr("BirthDate") = #1/15/1955#
        dr("HomeAddress") = "1234 A Street"
        dr("City") = "Los Angeles"
        dr("DeptId") = 1

        ' Add to the Rows collection.
        dtEmp.Rows.Add(dr)

        dr = dtEmp.NewRow()
        ' Set all the columns.
        dr("FirstName") = "Ann"
        dr("LastName") = "Doe"
        dr("BirthDate") = #1/15/1955#
        dr("HomeAddress") = "1234 A Street"
        dr("City") = "Los Angeles"
        dr("DeptId") = 1
        dtEmp.Rows.InsertAt(dr, 0)

        ' Read a semicolon-delimited text file into a DataTable.

        ' IMPORTANT: this works only if you copy the Employees.Dat
        ' file from the main project's directory to the BIN subdirectory

        ' Open the file, read its contents.
        Dim sr As New System.IO.StreamReader("employees.dat")
        Dim fileText As String = sr.ReadToEnd
        sr.Close()

        ' This regular expression defines a row of elements, and assigns a name
        ' to each group (that is, a field in the text row).
        Dim re As New System.Text.RegularExpressions.Regex("""(?<fname>[^""]+)"";""(?<lname>[^""]+)"";(?<bdate>[^;]+);""(?<addr>[^""]+)"";""(?<city>[^""]+)""")
        Dim ma As System.Text.RegularExpressions.Match

        dtEmp.BeginLoadData()
        For Each ma In re.Matches(fileText)
            ' A new line has been found, so add a row to the table.
            ' Create an array of values and add it in one operation
            Dim values() As Object = {ma.Groups("fname").Value, ma.Groups("lname").Value, _
                ma.Groups("bdate").Value, ma.Groups("addr").Value, ma.Groups("city").Value}
            dtEmp.LoadDataRow(values, True)
        Next
        dtEmp.EndLoadData()

        ' --- create the Department table

        ' Create the Departments table
        Dim dtDept As New DataTable("Departments")

        ' The DeptId file must be unique.
        With dtDept.Columns.Add("DeptId", GetType(Integer))
            .Unique = True
        End With
        ' The department Name must be unique as well.
        With dtDept.Columns.Add("Name", GetType(String))
            .MaxLength = 50
            .Unique = True
        End With
        ' Make dtDept the primary key of the table.
        dtDept.PrimaryKey = New DataColumn() {dtDept.Columns("DeptId")}

        ' Add to the DataSet.
        ds.Tables.Add(dtDept)

        ' Add a few rows.
        Dim deptValues() As Object = {1, "Sales"}
        dtDept.LoadDataRow(deptValues, True)
        ' You can do the same in just one statement.
        dtDept.LoadDataRow(New Object() {2, "Tech Support"}, True)
        dtDept.LoadDataRow(New Object() {3, "Marketing"}, True)

        ' Ensure that all Employees are associated to a department.
        Dim i As Integer
        For i = 0 To dtEmp.Rows.Count - 1
            ' Assign a DeptId value in the range 1-3.
            dtEmp.Rows(i).Item("DeptId") = CInt((i Mod 3) + 1)
        Next
        ds.AcceptChanges()

        ' show result in first grid
        DataGrid1.DataSource = dtDept
    End Sub

    ' convert some fields to uppercase

    Private Sub btnUppercase_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnUppercase.Click
        ' Get a reference to the Employees table.
        Dim dtEmp As DataTable = ds.Tables("Employees")

        Dim dr As DataRow
        For Each dr In dtEmp.Rows
            dr("FirstName") = dr("FirstName").ToString.ToUpper
            dr("LastName") = dr("LastName").ToString.ToUpper
        Next
    End Sub

    Private Sub btnEvents_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEvents.Click
        ' Demonstrate how to deal with events from Employees table.
        DataTable = ds.Tables(0)
    End Sub

    Dim WithEvents DataTable As DataTable

    ' All the DataTable event handlers -------

    Private Sub DataTable_ColumnChanging(ByVal sender As Object, ByVal e As System.Data.DataColumnChangeEventArgs) Handles DataTable.ColumnChanging
        Dim dt As DataTable = CType(sender, DataTable)
        Debug.WriteLine("Changing Column " & e.Column.ColumnName & " to " & e.ProposedValue.ToString)

        ' Show how you can reject a change in a column
        If e.Column.ColumnName = "BirthDate" Then
            If CDate(e.ProposedValue) > Date.Now Then
                'Throw New ArgumentException("Invalid birth date value")
                e.Row.SetColumnError(e.Column.ColumnName, "Invalid birth date value")
            End If
        End If
    End Sub

    Private Sub DataTable_ColumnChanged(ByVal sender As Object, ByVal e As System.Data.DataColumnChangeEventArgs) Handles DataTable.ColumnChanged
        Dim dt As DataTable = CType(sender, DataTable)
        Debug.WriteLine("Changed Column " & e.Column.ColumnName & " to " & e.Row(e.Column.ColumnName).ToString)
    End Sub

    Private Sub DataTable_RowChanging(ByVal sender As Object, ByVal e As System.Data.DataRowChangeEventArgs) Handles DataTable.RowChanging
        Dim dt As DataTable = CType(sender, DataTable)
        Debug.WriteLine("Changing Row (" & e.Action.ToString & ")")

        If e.Row("FirstName").ToString = "" And e.Row("LastName").ToString = "" Then
            'Throw New ArgumentException("FirstName and LastName can't be empty")
            e.Row.RowError = "First and last name can't be both null"
        End If
    End Sub

    Private Sub DataTable_RowChanged(ByVal sender As Object, ByVal e As System.Data.DataRowChangeEventArgs) Handles DataTable.RowChanged
        Dim dt As DataTable = CType(sender, DataTable)
        Debug.WriteLine("Changed Row (" & e.Action.ToString & ")")
    End Sub

    Private Sub DataTable_RowDeleting(ByVal sender As Object, ByVal e As System.Data.DataRowChangeEventArgs) Handles DataTable.RowDeleting
        Dim dt As DataTable = CType(sender, DataTable)
        Debug.WriteLine("Deleting Row")
    End Sub

    Private Sub DataTable_RowDeleted(ByVal sender As Object, ByVal e As System.Data.DataRowChangeEventArgs) Handles DataTable.RowDeleted
        Dim dt As DataTable = CType(sender, DataTable)
        Debug.WriteLine("Deleted Row")
    End Sub

    ' demonstrates the DataTable.Select method

    Private Sub btnSelect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSelect.Click
        ' Get a reference to the Employees table.
        Dim dtEmp As DataTable = ds.Tables("Employees")

        ' Copy only the structure of the Employees table in the new table.
        Dim newDt As DataTable = dtEmp.Clone()
        newDt.TableName = "YoungEmployees"

        ' Select a subset of all employees, sorted on their names.
        Dim drows() As DataRow = dtEmp.Select("DeptId IN (2,3)", "LastName, FirstName")
        ' Import the array of DataRows into the new table.
        Dim dr As DataRow
        For Each dr In drows
            newDt.ImportRow(dr)
        Next

        ' Now show the new table.
        DataGrid2.DataSource = newDt
    End Sub

    ' demonstrate the DataView object

    Private Sub btnDataView_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDataView.Click
        ' Get a reference to the Employees table.
        Dim dtEmp As DataTable = ds.Tables("Employees")

        ' Create a dataview on this table.
        Dim dv As New DataView(dtEmp)
        ' Set its filter and sort properties.
        dv.RowFilter = "BirthDate >= #1/1/1960#"
        dv.Sort = "LastName, FirstName"

        ' Display the dataview in a non-editable DataGrid.
        dv.AllowEdit = False
        DataGrid2.DataSource = dv
    End Sub

    Private Sub btnRelations_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRelations.Click
        ' Get a reference to the Employees and Department tables.
        Dim dtEmp As DataTable = ds.Tables("Employees")
        Dim dtDept As DataTable = ds.Tables("Departments")

        ' Now we can create the relation between the two tables.
        Dim relDeptEmp As New DataRelation("DeptEmp", dtDept.Columns("DeptId"), dtEmp.Columns("DeptId"))
        ds.Relations.Add(relDeptEmp)

        ' Display the names of the employees in the first department.
        Dim drEmployees() As DataRow = dtDept.Rows(0).GetChildRows("DeptEmp")
        Dim drEmp As DataRow
        For Each drEmp In drEmployees
            Debug.WriteLine(drEmp("CompleteName"))
        Next

        ' Display the number of employees in each department.
        Dim dr As DataRow
        For Each dr In dtDept.Rows
            Debug.WriteLine(dr("Name").ToString & ", " & _
                dr.GetChildRows("DeptEmp").Length.ToString)
        Next

        ' This statement returns the name of the department in the first employee.
        Dim drDepartment As DataRow = dtEmp.Rows(0).GetParentRow("DeptEmp")

        ' Add a calculated column to the Departments table
        ' that returns the number of employees for each department
        dtDept.Columns.Add("EmployeesCount", GetType(Integer), "Count(Child(DeptEmp).EmpID)")

        ' Add a new Bossid column to the Departments table, and fill it with the
        ' ID of the first 3 employees.
        dtDept.Columns.Add("BossId", GetType(Integer))
        Dim i As Integer
        For i = 0 To dtDept.Rows.Count - 1
            dtDept.Rows(i)("BossId") = dtEmp.Rows(i)("EmpId")
        Next
        dtDept.AcceptChanges()

        ' Create another relation between the Departments and Employees table.
        ds.Relations.Add("DeptBoss", dtEmp.Columns("EmpId"), dtDept.Columns("BossId"))

        ' Add a calcualted column to the Departments table that returns the boss's name.
        dtDept.Columns.Add("BossName", GetType(String), "Parent(DeptBoss).CompleteName")

        DataGrid1.DataSource = dtDept

    End Sub

    ' create constraints

    Private Sub btnConstraints_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConstraints.Click
        ' Get a reference to the Employees and Department tables.
        Dim dtEmp As DataTable = ds.Tables("Employees")
        Dim dtDept As DataTable = ds.Tables("Departments")

        ' Add a unique constraint on the (LastName, FirstName) column combination.

        ' Prepare the array of involved DataColumn objects.
        Dim cols() As DataColumn = {dtEmp.Columns("LastName"), _
            dtEmp.Columns("FirstName")}
        ' Create the UniqueConstraint object.
        Dim uc As New UniqueConstraint("UniqueName", cols)
        ' Add it to the table's Constraints collection.
        dtEmp.Constraints.Add(uc)

        ' Attempt to create duplicate names.
        Try
            ' Add a new record that contains duplicated values in (LastName, FirstName)
            Dim dr As DataRow = dtEmp.NewRow
            dr("FirstName") = dtEmp.Rows(0)("FirstName")
            dr("LastName") = dtEmp.Rows(0)("LastName")
            dr("DeptId") = 1
            dtEmp.Rows.Add(dr)
        Catch ex As Exception
            MessageBox.Show(ex.Message, "Unique constraint violation", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try

        ' Create a foreign key constraint

        If Not (ds.Relations("DeptEmp") Is Nothing) Then
            MessageBox.Show("You can't add a constraint after a relatin on the same columns")
            Exit Sub
        End If

        Dim fkrelDeptEmp As New ForeignKeyConstraint("FKDeptEmp", dtDept.Columns("DeptId"), dtEmp.Columns("DeptId"))
        dtEmp.Constraints.Add(fkrelDeptEmp)

        fkrelDeptEmp.DeleteRule = Rule.SetNull
        fkrelDeptEmp.UpdateRule = Rule.Cascade
        fkrelDeptEmp.AcceptRejectRule = AcceptRejectRule.None
    End Sub

    ' save the DataSet to XML

    Private Sub btnSaveXml_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSaveXml.Click
        'ds.Relations("DeptEmp").Nested = True

        With ds.Tables("Employees")
            .Namespace = "www.vb2themax.com"
            .Prefix = "emp"
        End With

        ds.WriteXml("c:\dataset.xml")
    End Sub

End Class