c# - Silverlight Hosted in Winforms

Question

I would like to host a silverlight control in winforms via a winforms browser, but for it to work I need some way for the forms to talk to the silverlight, and also the other way around. Would it be possible to somehow have the two interact with each other using JavaScript as a middleman? I.e., have the form speak to the browser's javascript, and have that speak to the silverlight control? Is there a better way? Or even a way at all? (other than compiling the code as silverlight and wpf)

Answer 1

I think using the Windows Forms WebBrowser control is your best bet. To do this, you'll need your Silverlight app on a webpage, then you point your WebBrowser at the page's URI.

To keep your WebBrowser control from acting like IE, I'd recommend setting the following:

webBrowser.AllowNavigation = false;
webBrowser.AllowWebBrowserDrop = false;
webBrowser.IsWebBrowserContextMenuEnabled = false;
webBrowser.WebBrowserShortcutsEnabled = false;

Calling methods on your form from within Silverlight is easy enough to do. To start, you need a class that has all the methods you want to call from Silverlight. You can use your form itself or another object, but you need to mark the class with the [ComVisible(true)] attribute. Then you assign your object to the WebBrowser.ObjectForScripting property. This exposes your object as "window.external" on the webpage.

[ComVisible(true)]
public partial class Form1 : Form
{
    ......
    webBrowser.ObjectForScripting = this;
    ......
    public void CallMeInForm(string something)
    {
        MessageBox.Show("Silverlight said: " + something);
    }
}

That's it for inside your Windows Forms project. Inside of your Silverlight app, you need to pick up this ObjectForScripting and invoke methods on it. To call the method in my example above, use the following lines:

using System.Windows.Browser;
......
ScriptObject myForm = (ScriptObject)HtmlPage.Window.GetProperty("external");
myForm.Invoke("CallMeInForm", "testing 1 2 3");

The Invoke command lets you pass any number and type of parameters to your function, although I suspect it wouldn't like it very much if you try passing complex datatypes around. But if you needed to do so, you could always use serialization.

Calling Silverlight functions from your form seems to be the tricker direction. I haven't figured this one out completely yet.

In your Silverlight app, you also expose functions to the webpage. To do this, use the HtmlPage.RegisterScriptableObject() function. Again, you can pass in any class with methods you want to expose. For a method to be exposed, though, you have to mark it with the [ScriptableMember] attribute.

HtmlPage.RegisterScriptableObject("Page", this);
......
[ScriptableMember]
public void CallMeInSilverlight(string message)
{
    HtmlPage.Window.Alert("The form said: " + message);
}

At this point, your method is exposed to JavaScript on the page and you could call it like so, assuming you added id="silverlightControl" to your <object> element:

document.getElementById('silverlightControl').Content.Page.CallMeInSilverlight("testing 1 2 3");

Notice the Page property? That's what the call to RegisterScriptableObject() gave us. Now, let's wrap this into a tidy JavaScript method:

<script type="text/javascript">
    function CallMe(message) {
        var control = document.getElementById('silverlightControl');
        control.Content.Page.CallMeInSilverlight(message);
    }
</script>

And now we can call the CallMe() method from the Windows Forms app like so:

public void CallToSilverlight()
{
    webBrowser.InvokeScript("CallMe", new object[] { "testing 1 2 3" });
}