e.Data.GetData casting problem in WinForms drag-and-drop

问题

i'm trying to make a drag-and-drop between 2 instances of my programs, but when i try to cast data to my type it throws an Invalid Cast Exception.

Here is the code:

    protected virtual void GetDropIEntities(DragEventArgs e)
    {

        foreach (string s in e.Data.GetFormats())
            Console.WriteLine(s);

        Entity[] myDroppedEnts = (Entity[])e.Data.GetData(e.Data.GetFormats()[0]);

    }

The weirdest thing is that Console.WriteLine writes "Entity[]" on the output, but when i try to cast the exception is thrown. Can someone give me a hand with this? Thx in advance!

回答1:

To drag and drop objects from one instance of an application to another, the object must be serializable. Otherwise, the cast will not work as expected.

To accomplish this, you can add the [Serializable] attribute to your Entity class, and optionally implement the ISerializable interface. For an introduction on how to make a class Serializable, see: http://msdn.microsoft.com/en-us/library/4abbf6k0(v=VS.90).aspx

This is the same issue with using the Clipboard. A great example can be seen on this CodeProject site:

http://www.codeproject.com/KB/cs/copycustomclasstoclipbrd.aspx

来源：https://stackoverflow.com/questions/7122987/e-data-getdata-casting-problem-in-winforms-drag-and-drop