Silverlight 4 DropDropBehavior and FileDragDropBehavior with Command Binding

Here is an easy to use FileDragDropBehavior that you can use in your XAML to implement dragging and dropping of files in your Silverlight 4 Application

	using System.IO;
	using System.Windows;
	using System.Windows.Input;
	using System.Windows.Interactivity;
	/// <summary>
	/// A simple file drag and drop behavior.
	/// </summary>
	public class FileDragDropBehavior : DragDropBehavior<FileInfo[]>
	{
	/// <summary>
	/// The <see cref="FilesDroppedCommand" /> dependency property's name.
	/// </summary>
	public const string FilesDroppedCommandPropertyName = "FilesDroppedCommand";
	/// <summary>
	/// Gets or sets the value of the <see cref="FilesDroppedCommand" />
	/// property. This is a dependency property.
	/// </summary>
	public ICommand FilesDroppedCommand
	{
	get
	{
	return (ICommand)GetValue(FilesDroppedCommandProperty);
	}
	set
	{
	SetValue(FilesDroppedCommandProperty, value);
	}
	}
	/// <summary>
	/// Identifies the <see cref="FilesDroppedCommand" /> dependency property.
	/// </summary>
	public static readonly DependencyProperty FilesDroppedCommandProperty = DependencyProperty.Register(
	FilesDroppedCommandPropertyName,
	typeof(ICommand),
	typeof(FileDragDropBehavior),
	new PropertyMetadata(null));
	/// <summary>
	/// Determines if this drop event should run.
	/// </summary>
	/// <param name="sender">The sender.</param>
	/// <param name="e">The <see cref="System.Windows.DragEventArgs"/> instance containing the event data.</param>
	/// <returns>True if the event should run, otherwise false</returns>
	protected override bool ShouldDropEventRun(object sender, DragEventArgs e)
	{
	return this.FilesDroppedCommand != null;
	}
	/// <summary>
	/// Called when [dropped data].
	/// </summary>
	/// <param name="files">The files.</param>
	protected override void OnDroppedData(FileInfo[] files)
	{
	if (files == null)
	return;
	if (this.FilesDroppedCommand.CanExecute(files))
	this.FilesDroppedCommand.Execute(files);
	}
	/// <summary>
	/// Gets the data string.
	/// </summary>
	/// <returns></returns>
	protected override string GetDataString()
	{
	return DataFormats.FileDrop;
	}
	}
	public abstract class DragDropBehavior<TData> : Behavior<FrameworkElement>
	{
	protected override void OnAttached()
	{
	AssociatedObject.AllowDrop = true;
	AssociatedObject.Drop += AssociatedObject_Drop;
	base.OnAttached();
	}
	protected override void OnDetaching()
	{
	AssociatedObject.Drop -= AssociatedObject_Drop;
	base.OnDetaching();
	}
	protected void AssociatedObject_Drop(object sender, DragEventArgs e)
	{
	if(!ShouldDropEventRun(sender, e))
	return;
	var dataName = GetDataString();
	if(!e.Data.GetDataPresent(dataName))
	return;
	var data = (TData)e.Data.GetData(dataName);
	OnDroppedData(data);
	}
	/// <summary>
	/// Called when [dropped data].
	/// </summary>
	/// <param name="data">The data.</param>
	protected abstract void OnDroppedData(TData data);
	/// <summary>
	/// Determines if a drop event should run; use this to check for null values and what-not.
	/// </summary>
	/// <param name="sender">The sender.</param>
	/// <param name="e">The <see cref="System.Windows.DragEventArgs"/> instance containing the event data.</param>
	/// <returns>True if should run, otherwise false</returns>
	protected virtual bool ShouldDropEventRun(object sender, DragEventArgs e)
	{
	return true;
	}
	/// <summary>
	/// When overriden, gets the data string to call e.Data.GetData(...) with.
	/// </summary>
	/// <returns>The data string to call GetData(...) with.</returns>
	protected abstract string GetDataString();
	}

view raw DragDropBehaviours.cs hosted with ❤ by GitHub

	<Border
	Width="300"
	Height="200"
	Margin="0 20 0 20"
	Background="LightGray"
	x:Name="DropArea">
	<i:Interaction.Behaviors>
	<con:FileDragDropBehavior
	FilesDroppedCommand="{Binding FilesDroppedCmd}" />
	</i:Interaction.Behaviors>
	<TextBlock
	FontWeight="Bold" FontSize="20"
	HorizontalAlignment="Center"
	VerticalAlignment="Center"
	Text="Drag Files Here" />
	</Border>

view raw DragDropExampleXaml.xaml hosted with ❤ by GitHub

Just put the class in your project, reference the namespace in your XAML file and add the behavior to where you want to drop a file.

Jacob