I'm writting Custom DataGRid in VB.NET.

Question

Public Class Form1

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

'Required by the Windows Form Designer

Private components As System.ComponentModel.IContainer

'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.

Friend WithEvents dataGrid1 As System.Windows.Forms.DataGrid

<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()

Me.dataGrid1 = New System.Windows.Forms.DataGrid

CType(Me.dataGrid1, System.ComponentModel.ISupportInitialize).BeginInit()

Me.SuspendLayout()

'

'dataGrid1

'

Me.dataGrid1.DataMember = ""

Me.dataGrid1.HeaderForeColor = System.Drawing.SystemColors.ControlText

Me.dataGrid1.Location = New System.Drawing.Point(8, 72)

Me.dataGrid1.Name = "dataGrid1"

Me.dataGrid1.Size = New System.Drawing.Size(592, 192)

Me.dataGrid1.TabIndex = 0

'

'Form1

'

Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)

Me.ClientSize = New System.Drawing.Size(616, 286)

Me.Controls.Add(Me.dataGrid1)

Me.Name = "Form1"

Me.Text = "Form1"

CType(Me.dataGrid1, System.ComponentModel.ISupportInitialize).EndInit()

Me.ResumeLayout(False)

End Sub

#End Region

'Public Class Form1

'Inherits System.Windows.Forms.Form

Protected myDataSet As New DataSet

Private strConn = "Data Source=vnis03\tuaba;User ID=sa;Password=blank;Initial Catalog=northwind"

Private strComm = "select * From Customers"

Private sqlConn As System.Data.SqlClient.SqlConnection

Private sqlDA As System.Data.SqlClient.SqlDataAdapter

Private dgts As New DataGridTableStyle

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

sqlConn = New System.Data.SqlClient.SqlConnection(strConn)

sqlDA = New System.Data.SqlClient.SqlDataAdapter(strComm, sqlConn)

sqlDA.Fill(Me.myDataSet, "Cus")

Me.dataGrid1.SetDataBinding(Me.myDataSet, "Cus")

dgts.MappingName = "Cus"

For j As Integer = 0 To Me.myDataSet.Tables("Cus").Columns.Count - 1

Dim textBoxColumn As New System.Windows.Forms.DataGridTextBoxColumn

textBoxColumn.MappingName = Me.myDataSet.Tables("Cus").Columns(j).ColumnName

textBoxColumn.HeaderText = Me.myDataSet.Tables("Cus").Columns(j).ColumnName

textBoxColumn.Width = 100

dgts.GridColumnStyles.Add(textBoxColumn)

Next

Me.dataGrid1.TableStyles.Add(dgts)

End Sub

Private Sub PaintCell(ByVal sender As Object, ByVal e As MouseEventArgs)

' Use the HitTest method to get a HitTestInfo object.

Dim hi As DataGrid.HitTestInfo

Dim grid As DataGrid = CType(sender, DataGrid)

hi = grid.HitTest(e.X, e.Y)

' Test if the clicked area was a cell.

If hi.Type = DataGrid.HitTestType.Cell Then

' If it's a cell, get the GridTable and ListManager of the

' clicked table.

Dim dgt As DataGridTableStyle = dataGrid1.TableStyles(0)

Dim cm As CurrencyManager = CType(Me.BindingContext _

(myDataSet.Tables(dgt.MappingName)), CurrencyManager)

' Get the Rectangle of the clicked cell.

Dim cellRect As Rectangle

cellRect = grid.GetCellBounds(hi.Row, hi.Column)

' Get the clicked DataGridTextBoxColumn.

Dim gridCol = CType(dgt.GridColumnStyles(hi.Column), MyGridColumn)==> bugs

'gridCol.GetType()

' get the graphics object for the form.

Dim g As Graphics = dataGrid1.CreateGraphics()

' Create two new Brush objects: a fore brush and back brush.

Dim fBrush As New SolidBrush(Color.Blue)

Dim bBrush As New SolidBrush(Color.Yellow)

' Invoke the Paint method to paint the cell with the brushes.

gridCol.PaintCol(g, cellRect, cm, hi.Row, bBrush, fBrush, False)

End If

End Sub 'PaintCell

'End Class 'Form1

Private Sub dataGrid1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles dataGrid1.MouseDown

Me.PaintCell(sender, e)

End Sub

End Class

Public Class MyGridColumn

Inherits System.Windows.Forms.DataGridTextBoxColumn

Public Sub PaintCol(ByVal g As Graphics, ByVal cellRect As Rectangle, _

ByVal cm As CurrencyManager, ByVal rowNum As Integer, ByVal bBrush As Brush, _

ByVal fBrush As Brush, ByVal isVisible As Boolean)

Me.Paint(g, cellRect, cm, rowNum, bBrush, fBrush, isVisible)

End Sub

End Class





Now, i have problem with statement:
 

gridCol = CType(dgt.GridColumnStyles(hi.Column), MyGridColumn)

And, when i click a cell, i've delivered message: "Additional information: Specified cast is not valid."