override DataGrid.BeginInit ()

I need to override DataGrid.BeginInit() (and DataGrid.EndInit()). They are
inherited from the interface ISupportsInitialize.

Here's how the documentation declares BeginInit:

public virtual void BeginInit();

But when the following code:

public class MyDataGrid : DataGrid {
public override void BeginInit () {}
}

produces this compiler error:

'MyDataGrid.BeginInit()' : cannot override inherited member
'System.Windows.Forms.DataGrid.BeginInit()' because it is not marked
virtual, abstract, or override

What am I missing?

Thanks!
Kristin