System.Runtime.InteropServices.COMException when trying to drag and drop between two WPF applications

Question

System.Runtime.InteropServices.COMException when trying to drag and drop between two WPF applications

I have made a WPF application that allows drag and drop of instances of a class I made (FakeNodeViewModel). It works fine when I work with only one instance of my application. But when I use 2 and I try to drag objects from one and drop on the other, I get an exception when dropping:

System.Runtime.InteropServices.COMException: 'Tymed non valide (Exception de HRESULT : 0x80040069 (DV_E_TYMED))'

and the two instances crash. My method to handle drop starts like this:

private void grid_Drop(object sender, DragEventArgs e) {
        if (e.Data.GetDataPresent("fakeNode")) {
            var fakeNodeViewModel = (FakeNodeViewModel)e.Data.GetData("fakeNode");

and the program crash at var fakeNodeViewModel = (FakeNodeViewModel)e.Data.GetData("fakeNode"); I didn't find a lot about this. Does anyone know what happen and how to solve it ?

c#

wpf

drag-and-drop

asked on Stack Overflow Aug 28, 2020 by

Kantine

2 Answers

You should decorate the FakeNodeViewModel class with the System.SerializableAttribute for it be COM serializable:

[Serializable]
public class FakeNodeViewModel
{
    ...
}

answered on Stack Overflow Aug 28, 2020 by

mm8

Thanks mm8 for your answer. Indeed, I had to add [Serializable] attribute to my FakeNodeViewModel class. Then I had to do my drag drop like this:

drag:

private void MoveFakeNode(object sender, MouseEventArgs e) {
            if (e.LeftButton == MouseButtonState.Pressed) {
                // Current mouse position
                var fakeNodeViewModel = (FakeNodeViewModel)((FrameworkElement)e.OriginalSource).DataContext;
                var dataObject = new DataObject(DataFormats.Serializable, fakeNodeViewModel);
                DragDrop.DoDragDrop((DependencyObject)e.Source, dataObject, DragDropEffects.Copy);
            }
        }

drop:

private void grid_Drop(object sender, DragEventArgs e) {
    if (e.Data.GetDataPresent(DataFormats.Serializable)) {
        // Get the fake node
        var fakeNodeViewModel =(FakeNodeViewModel)e.Data.GetData(DataFormats.Serializable);
        ...
    }
}

And I was able to get my data from the other instance.

answered on Stack Overflow Aug 28, 2020 by

Kantine

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