Public Class Form1
   Inherits Form
   Protected dataGrid1 As DataGrid
    
   Private Sub GetPreferredHeight()
      Dim g As Graphics
      g = Me.CreateGraphics()
      Dim gridPreferredHeight As Integer
      Dim myTextColumn As MyGridColumn
      ' Assuming column 1 of a DataGrid control is a 
      ' DataGridTextBoxColumn.
      myTextColumn = CType(dataGrid1.TableStyles(0). _
      GridColumnStyles(1), MyGridColumn)
      Dim myVal As String
      myVal = "A long string value"
      gridPreferredHeight = myTextColumn.GetPrefHeight _
      (g, myVal)
      Console.WriteLine(gridPreferredHeight)
   End Sub 
End Class 

Public Class MyGridColumn
Inherits DataGridTextBoxColumn
   public Function GetPrefHeight(g As Graphics , val As string) _
   As Integer
      return me.GetPreferredHeight(g, val)
   End Function
End Class