Help Autosizing columns of the datagrid

[mAdMaLuDaWg]

Hello All,
I'm trying to autosize the columns of my datagrid using the following code, there seems to be a bug that I can't get rid of.

Public Sub AutoSizeCol(ByVal dGrid As DataGrid, ByVal strTableName As String)

Dim width As Decimal
Dim sf As StringFormat
Dim g As Graphics
Dim numRows As Integer
Dim numCols As Integer
Dim size As SizeF
Dim I, J As Integer



numRows = CType(dGrid.DataSource.tables(strTableName), DataTable).Rows.Count
numCols = CType(dGrid.DataSource.tables(strTableName), DataTable).Columns.Count


myGridColumnStylesCollection = dGrid.TableStyles(0).GridColumnStyles

g = Graphics.FromHwnd(dGrid.Handle)
sf = New StringFormat(StringFormat.GenericTypographic)


For I = 0 To numCols

For J = 0 To numRows

size = g.MeasureString(dGrid(J, I), dGrid.Font, 500, sf)
If (size.Width > width) Then width = size.Width
dGrid.TableStyles(strTableName).GridColumnStyles(I).Width = CType(width, Integer)
Next
Next

g.Dispose()

End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
DataSet1.ReadXml("..\XML\ConditionCode.xml")
dgrdConditionCode.DataMember = DataSet1.Tables(0).TableName
AutoSizeCol(dgrdConditionCode, DataSet1.Tables(0).TableName)
End Sub

I get the following error from the following line:
dGrid.TableStyles(strTableName).GridColumnStyles(I).Width = CType(width, Integer) --> object Reference Not set to instant of object


Any help would be greatly appreciated.

[Iouri]

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        AutoSizeTable()'autosize all cols
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        AutoSizeCol(1)'autosize 1st col
    End Sub


Public Sub AutoSizeTable()
        Dim numCols As Integer
        numCols = CType(dg.DataSource, DataTable).Columns.Count
        Dim i As Integer
        i = 0
        Do While (i < numCols)
            AutoSizeCol(i)
            i = (i + 1)
        Loop

    End Sub

    Public Sub AutoSizeCol(ByVal col As Integer)

        Dim width As Single
        width = 0
        Dim numRows As Integer
        numRows = CType(dg.DataSource, DataTable).Rows.Count
        Dim g As Graphics
        g = Graphics.FromHwnd(dg.Handle)
        Dim sf As StringFormat
        sf = New StringFormat(StringFormat.GenericTypographic)
        Dim size As SizeF
        Dim i As Integer
        i = 0

        Do While (i < numRows)
            size = g.MeasureString(dg(i, col).ToString, dg.Font, 500, sf)
            If (size.Width > width) Then
                width = size.Width
            End If
            i = (i + 1)

        Loop
        g.Dispose()
        dg.TableStyles("customers").GridColumnStyles(col).Width = CType(width, Integer)

    End Sub

[mAdMaLuDaWg]

Thank you for the reply Iouri. However, I am using multiple datagrids in my program and would like to create a generic function for all datagrids.
Could you help me fix my code?