How to hide the context menu when you click the header cells in the WinForms GridControl?

//Event triggered from Form_load
this.contextMenuStripEx1.Opening += contextMenuStripEx1_Opening;
void contextMenuStripEx1_Opening(object sender, CancelEventArgs e)
{
    int R_index = this.gridControl1.CurrentCell.RowIndex;
    int C_index = this.gridControl1.CurrentCell.ColIndex;
    if (R_index == 0 || C_index == 0)
        //ContextMenuStrip removed for headers
        e.Cancel = true;
     else
        e.Cancel = false;
}

'Event triggered from Form_load
AddHandler Me.contextMenuStripEx1.Opening, AddressOf contextMenuStripEx1_Opening 
Private Sub contextMenuStripEx1_Opening(ByVal sender As Object, ByVal e As CancelEventArgs)
    Dim R_index As Integer = Me.gridControl1.CurrentCell.RowIndex
    Dim C_index As Integer = Me.gridControl1.CurrentCell.ColIndex
    If R_index = 0 OrElse C_index = 0 Then
      'ContextMenuStrip removed for headers
       e.Cancel = True
    Else
       e.Cancel = False
    End If
End Sub