Cross-Process Drag and Drop of custom object type in WinForms C#
c#, drag-and-drop, iserializable, winforms
Solution
You are crossing a process boundary, object references are not valid in another process. The DataObject class supports serializing objects to get them across the wall, it uses BinaryFormatter. So, yes, you'll need to apply the [Serializable] attribute to your class and make sure your objects can de/serialize properly.
Problem
This question is close to what I'm interested in, but not quite. I have a .NET WinForms application written in C#. I have a `ListView` control which displays an array of C# objects. I've hooked it up so that you can drag/drop these listview items to a different form in the same application, and it properly passes the array of objects (type `Session`) to the drop handler for that other form. However, I now want to support cross-process drag/drop where I run multiple instances of my application. This appears that it's going to work (e.g. `GetDataPresent` succeeds), but ultimately throws an exception when I actually try to retrieve the data-- cannot cast `object[]` to `Session[]`. ``` if (e.Data.GetDataPresent("Fiddler.Session[]")) { Session[] oDroppedSessions; try { oDroppedSessions = (Session[])e.Data.GetData("Fiddler.Session[]"); } catch (Exception eX) { // reaches here } } ``` Anyone know if I must implement `ISerializable` for my objects in order to make this work? Ordinarily, I'd simply try it, but implementing `ISerializable` for this class would be quite non-trivial, and I'm worried that there may be weird side-effects of doing so. UPDATE: Implementing `ISerializable` doesn't help-- the method is never called. Similarly, adding the `Serializable` attribute to the class has no impact at all. Any other ideas?