public override object PrepareCellForEdit(FrameworkElement editingElement)
{
// compose all the values into a list of objects
List<object> values = new List<object>();
var children = (editingElement as Panel).Children;
//for (int i = 0; i < InnerColumns.Count; i++)
//{
// var value = InnerColumns[i].PrepareCellForEdit(children[i] as FrameworkElement);
// values.Add(value);
//}
return values;
}