Silverlight – Dynamically Loading an Assembly

Just something that someone asked me about today so sharing here. Imagine that you want to define a portion of your Silverlight application but leave some other piece to run time.

For example - a calculation engine or perhaps something more complicated like a piece of UI with interaction.

You can dynamically load up a .NET assembly in Silverlight at runtime, pull out known types from it and interact with them just like you would in any other .NET application.

I made my example as simple as possible. I defined a core UI which looks like this;

The idea is that the red bit is the "host" and the yellow bit is for the plug-in editor. I define an interface to live between my host and my plug-in editor;

  public class TextEventArgs : EventArgs  {    public string TheText { get; set; }  }  public interface IEditUI  {    UIElement GetControls();    void SetText(string text);    event EventHandler<TextEventArgs> TextChanged;  }

 

and then an implementation of that which I put into an assembly called Implementation which is not referenced by my Silverlight application.

  public class Editor : IEditUI  {    public Editor()    {      textBox = new TextBox();    }    public UIElement GetControls()    {      StackPanel stackPanel = new StackPanel();      stackPanel.Margin = new Thickness(5);      stackPanel.Orientation = Orientation.Horizontal;      textBox = new TextBox();      textBox.Width = 100;      Button button = new Button();      button.Content = "Click Me";      button.Click += OnButtonClick;      stackPanel.Children.Add(textBox);      stackPanel.Children.Add(button);      return (stackPanel);    }    void OnButtonClick(object sender, RoutedEventArgs e)    {      if (TextChanged != null)      {        TextChanged(this, new TextEventArgs() { TheText = textBox.Text });      }          }    public void SetText(string text)    {      textBox.Text = text;    }    private TextBox textBox;       public event EventHandler<TextEventArgs> TextChanged;  }

 

Then, at runtime I can write code which will load this up and make use of it as in;

  public partial class Page : UserControl  {    public Page()    {      InitializeComponent();    }    void OnLoadDynamicEditor(object sender, EventArgs args)    {      WebClient client = new WebClient();      client.OpenReadCompleted += new OpenReadCompletedEventHandler(OnAssemblyOpened);      client.OpenReadAsync(new Uri("Implementation.dll", UriKind.Relative));    }    void OnAssemblyOpened(object sender, OpenReadCompletedEventArgs e)    {      AssemblyPart assemblyPart = new AssemblyPart();      Assembly assembly = assemblyPart.Load(e.Result);      editor = assembly.CreateInstance("Implementation.Editor") as IEditUI;      if (editor != null)      {        hostGrid.Children.Add(editor.GetControls());        editor.TextChanged += OnEditorTextChanged;      }         }    void OnSendToEditor(object sender, EventArgs args)    {      if (editor != null)      {        editor.SetText(txtHost.Text);      }    }    void OnEditorTextChanged(object sender, TextEventArgs e)    {      txtHost.Text = e.TheText;    }    IEditUI editor;  }

 

Note: The Implementation.dll assembly needs to be manually copied to the ClientBin folder of the website project in order for this to work.