I am currently creating two data templates one for single selected item from drag source and another for multiple selected items drag source and assigning thses templates to dragtemplate of drag source on drag start event.

but this is not working for me please let me know if there is any suggestion.

my drag start event code.

private void AssociatedObject_DragStart(object sender, DragDropStartEventArgs e)
{
DragSource dragsource = sender as DragSource ;
var dragNodes = new List<TreeNode>();

//
// TreeGrid has both "Selected Items" and an "Active Item".
// "Selected Items" only seems to be non-null when more than one item is selected.
// "Active Item" is non-null when at least one item is highlighted.
//
if (_dataPresenter.SelectedItems?.Any() ?? false)
{
foreach (var selectedRecord in _dataPresenter.SelectedItems)
{
if (selectedRecord is DataRecord dr &&
dr.DataItem is TreeNode node)
{
dragNodes.Add(node);
}
else if (selectedRecord is Cell c &&
c.Record is DataRecord drc &&
drc.DataItem is TreeNode nodec)
{
dragNodes.Add(nodec);
}
}
}
else if (_dataPresenter.ActiveRecord != null)
{
if (_dataPresenter.ActiveRecord is DataRecord dr &&
dr.DataItem is TreeNode node)
{
dragNodes.Add(node);
}
}

//
// Drag is only allowed if all nodes allow it.
//
dragsource.DragTemplate = DragSingleElementTemplate;
if (dragNodes.Any() &&
dragNodes.All(n => n.Attributes.HasFlag(TreeNodeAttributes.Drag)))
{
e.Data = dragNodes.ToArray();
if (dragNodes.Count>1)
{
dragsource.DragTemplate = DragMultipleElementTemplate;
}
}
else
{
e.Cancel = true;
}
dragsource.DragTemplate.LoadContent();
}