Data loss during WPF clipboard operations

Question

I am working with a FlowDocument in a WPF RichTextBox. Some of the flow document elements are created using subclasses of the System.Windows.Documents framework classes and all of the elements use the Tag property to store additional data.

If I use a XamlWriter to serialize a document tree, everything is correctly reflected in the resulting Xaml output.

However, if I simply copy and paste within the RichTextBox, although the pasted elements are visually identical to those from which they were copied, the clipboard operation discards all my additional data. Specifically, all the subclassed elements are pasted as instances of their base framework types and none of them have data in their Tag property.

This suggests that a WPF clipboard operation on a RichTextBox does not use XamlWriter for serialization, despite the fact that the serialized clipboard data identifies its format as "Xaml".

I imagine that the reason for this behavior is to ensure a common denominator when pasting into other Xaml-aware applications that do not necessarily have knowledge of my custom types. But I need to implement a richer copy / paste mechanism for use within my application.

I guess I can probably intercept the copy event and add clipboard data in a custom format, which is subsequently applied in the paste event. However, this presents its own complications, as elements may need to be wrapped before pasting (for example inline elements that are pasted into a block element context).

So, I am hoping to avoid reinventing the wheel and would appreciate any advice on how to get this to work using the existing framework infrastructure.

Many thanks, Tim

Answer 1

I don't have an exact answer to your question but I can think of two ways to proceed with -

1. Associate a CommandBinding for Copy/Paste operation, with your controls and perform custom operations in Execute and CanExecute methods. As explained here:

   http://msdn.microsoft.com/en-us/library/system.windows.input.commandbinding.aspx

2. Use DataObject class to intercept the Copy/Paste events and perform your custom operation there. i.e. DataObject.AddCopyingHandler and DataObject.AddPastingHandler.

   Some useful links -

   http://msdn.microsoft.com/en-us/library/system.windows.dataobject_members.aspx

   http://blogs.msdn.com/b/prajakta/archive/2006/11/28/auto-detecting-hyperlinks-in-richtextbox-part-ii.aspx

Hope that will help.