Fix #3482: Drag and Drop is no longer working in the Assemblies tree view.

ICSharpCode.ILSpyX/TreeView/PlatformAbstractions/IPlatformDataObject.cs

@@ -4,7 +4,7 @@
 	{
 		bool GetDataPresent(string format);
 		object GetData(string format);
-
 		void SetData(string format, object data);
+		object UnderlyingDataObject { get; }
 	}
 }

ICSharpCode.ILSpyX/TreeView/PlatformAbstractions/IPlatformDragDrop.cs

@@ -2,6 +2,6 @@
 {
 	public interface IPlatformDragDrop
 	{
-		XPlatDragDropEffects DoDragDrop(object dragSource, object data, XPlatDragDropEffects allowedEffects);
+		XPlatDragDropEffects DoDragDrop(object dragSource, IPlatformDataObject data, XPlatDragDropEffects allowedEffects);
 	}
 }

ILSpy/Controls/TreeView/WpfWindowsDataObject.cs

@@ -4,7 +4,7 @@ using ICSharpCode.ILSpyX.TreeView.PlatformAbstractions;
 
 namespace ICSharpCode.ILSpy.Controls.TreeView
 {
-	public class WpfWindowsDataObject : IPlatformDataObject
+	public sealed class WpfWindowsDataObject : IPlatformDataObject
 	{
 		private readonly IDataObject _dataObject;
 
@@ -27,5 +27,7 @@ namespace ICSharpCode.ILSpy.Controls.TreeView
 		{
 			_dataObject.SetData(format, data);
 		}
+
+		object IPlatformDataObject.UnderlyingDataObject => _dataObject;
 	}
 }

ILSpy/Controls/TreeView/WpfWindowsDragDropManager.cs

@@ -6,9 +6,9 @@ namespace ICSharpCode.ILSpy.Controls.TreeView
 {
 	public class WpfWindowsDragDropManager : IPlatformDragDrop
 	{
-		public XPlatDragDropEffects DoDragDrop(object dragSource, object data, XPlatDragDropEffects allowedEffects)
+		public XPlatDragDropEffects DoDragDrop(object dragSource, IPlatformDataObject data, XPlatDragDropEffects allowedEffects)
 		{
-			return (XPlatDragDropEffects)DragDrop.DoDragDrop(dragSource as DependencyObject, data, (DragDropEffects)allowedEffects);
+			return (XPlatDragDropEffects)DragDrop.DoDragDrop(dragSource as DependencyObject, data.UnderlyingDataObject, (DragDropEffects)allowedEffects);
 		}
 	}
 }