Question

I’m having an issue involving the following scenario, Application A has a DataGridView, from which objects are selected. They are dragged into a DataGridView inside Application B, and the objects are copied into the new list. Here is the code in App A, preparing the dragdrop:

       ArrayList ToDrag = this.GetSelectedBoundItems();
       DataObject data = new DataObject(ToDrag);
       this.DoDragDrop(data, DragDropEffects.Move | DragDropEffects.Copy);

The problem: the recieving end is unable to get the ArrayList. Here is the code for that:

 //formats has the value of "System.Collections.ArrayList"
 var formats = myRetrievedObject.GetFormats();

 //candoit has the value "true"
 var candoit = myRetrievedObject.GetDataPresent(typeof(ArrayList));

 //DraggedItems is of type "System.__ComObject"
 var DraggedItems = myRetrievedObject.GetData(typeof(ArrayList));

 //this returns null.  I 'think' this should work
 ArrayList DraggedItems2 = myRetrievedObject.GetData(typeof(ArrayList)) as ArrayList;

 //This throws an exception (see below)
 ArrayList DraggedItems2 = (ArrayList)myRetrievedObject.GetData(typeof(ArrayList)) as ArrayList;

This used to work. Two things have happened to this, we jumped from .net 2.0 to .net 4.0, and this code was translated into C++.net into C#.

I’m not sure what I’m missing. That data is supposed to be translated into an array list.

Thanks for the help!

edit this is the exception text from the cast

A first chance exception of type ‘System.InvalidCastException’ occurred in dfResultsControls.dll

Additional information: Unable to cast COM object of type ‘System.__ComObject’ to class type ‘System.Collections.ArrayList’. Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface.

Answer 1

Making the (data) object serializable solves the problem for me.