Public Class Form1
   Inherits Form
   Protected dataGrid1 As DataGrid
    

   Private Sub GetHeight()
      Dim myGridColumn As MyGridColumn
      ' Get a DataGridColumnStyle of a DataGrid control.
      myGridColumn = CType(dataGrid1.TableStyles(0). _
      GridColumnStyles("CompanyName"), myGridColumn)
      ' Create a Graphics object.
      Dim g As Graphics = Me.CreateGraphics()
      Dim s As Size = myGridColumn.GetPrefSize(g, "A string")
   End Sub 

End Class 

Public Class MyGridColumn
Inherits DataGridTextBoxColumn
   public Function GetPrefSize(g As Graphics , _
   thisString As String ) As Size
      return me.GetPreferredSize(g,thisString)
   End Function
End Class