internal void BeginEdit(RoutedEventArgs e)
{
Debug.Assert(!IsEditing, "Should not call BeginEdit when IsEditing is true.");
IsEditing = true;
DataGridColumn column = Column;
if (column != null)
{
// Ask the column to store the original value
column.BeginEdit(Content as FrameworkElement, e);
}
RaisePreparingCellForEdit(e);
}