Today, I discovered that DragExecutionMode.Legacy is not compatible with RadGridView Grouping and Column Resizing. To reproduce the error, put this code in the MainPage constructor or anywhere so that it executes before the user interacts with the Grid.
RadDragAndDropManager.ExecutionMode = DragExecutionMode.Legacy;
1. Drag a column header from the RadGridView into the Grouping area at the top.
2. Now resize any of the remaining columns.
3. [Unhandled Exception]
I'm not sure what our workaround will be because we need this setting for Auto-Scrolling in a ChildWindow that is doing Drag and Drop. Any ideas?