Silverlight 4: Drag and drop from desktop or image

Ok, Silverlight 4 is here and everyone's very happy and excited (well.. I think it's just more fun now to use Silverlight - especially with the nice toolkit, which can be found on codeplex). Yesterday I tried one of the new features and wow, it was pretty easy to implement drag and drop for Silverlight 4 applications.

So let's say you got a Listbox, like the following one

<ListBox x:Name="myListBox" />

Now you have to add e few things:

• Allow Drop with AllowTrop="True"
• An eventhandler for the Drop event
• And finally if you want eventhandlers for DragEnter and DragLeave

The whole thing should look like the following

<ListBox Name="myListBox" 
         AllowDrop="True" 
         Drop="myListBox_Drop" 
         DragEnter="myListBox_DragEnter" 
         DragLeave="myListBox_DragLeave" />

Lets talk about the "Drop" event for a moment. Drop supplies the event handler with the arguments from DragEventArgs: Take a look at it on MSDN. Here's how I handle the event

private void myListBox_Drop(object sender, DragEventArgs e)
{
 FileInfo[] droppedFiles = e.Data.GetData(DataFormats.FileDrop) as FileInfo[];

 for (int i = 0; i < droppedFiles.Length; i++)
 {
  this.myListBox.Items.Add(droppedFiles[i].Name);
                /* you have to access the data in the listbox via droppedFiles[i].OpenRead()
                   things like File.OpenRead(droppedFiles[i].FullName) won't work because
                   of the Silverlight 4 security model */
 }

 e.Handled = true;
}

Additionally you can use the DragEnter and DragLeave event to alert the user, that dragged files can be dropped on the object - just change the background colour or something like that (a border is quite nice as well).