How to call javascript function on a Silverlight 3 object?

I have the following Silverlight control defined:

<object id="objImageViewer" data="data:application/x-silverlight-2," type="application/x开发者_如何学Go-silverlight-2" width="100%" height="500px">
    <param name="source" value="../ClientBin/SomeImageViewer.xap"/>
    <param name="onError" value="onSilverlightError" />
    <param name="background" value="white" />
    <param name="minRuntimeVersion" value="3.0.40624.0" />
    <param name="autoUpgrade" value="true" />
    <param name="windowless" value="true" />
    <param name="initParams"
        value="
            Username=<%= ImageViewerUsername %>,
            Editable=<%= ImageViewerEditable ? "1" : "0" %>,
            Align=<%= ImageViewerAlign ? "1" : "0" %>
            " />
    <a href="http://go.microsoft.com/fwlink/?LinkID=149156&v=3.0.40624.0" style="text-decoration:none">
        <img src="http://go.microsoft.com/fwlink/?LinkId=108181" alt="Get Microsoft Silverlight" style="border-style:none"/>
    </a>
</object>

I have exposed the following method in my Silverlight control (Page.xaml.cs) to be accessible to Javascript:

[ScriptableMember]
public bool HasPendingUpdates()
{
    return btnSave.IsEnabled;
}

I then have a Javascript test function in my aspx page that is trying to do something with it:

var imageViewer = $("#objImageViewer")[0];
if (imageViewer.Content.Page.HasPendingUpdates())
{
    alert("Pending Changes Exist!");
}
else
{
    alert("NO Pending Changes Exist!");
}

Problem is that it fails after the Content object. I have tested the following:

var imageViewer = $("#objImageViewer")[0];

imageViewer // Valid
imageViewer.Content // Valid
imageViewer.Content.Page  // Invalid
imageViewer.Content.HasPendingUpdates()  // Invalid

So I am not sure what I am doing wrong. How do I get to the function within Content?

I am using IE8, Silverlight 3, ASP.NET. The silverlight control is created with the object tag as I don't think the control is an option in Silverlight 3+.

Any help would be much appreciated.

You need to register with Silverlight HTMLBridge an identifier to expose on the Content property and give it an object that has some scriptable entry points.

I tend to do this in the Page constructor:-

public Page()
{
     InitializeComponent();
     HtmlPage.RegisterScriptableObject("Page", this);
}

Now your code should work.

I have this Silverlight application structure:

public partial class App : Application
{
    private void Application_Startup(object sender, StartupEventArgs e)
    {
        Page uploadControl = new Page();
        // ...
        HtmlPage.RegisterScriptableObject("uploadControl", uploadControl);
    }
}

[ScriptableType]
public partial class Page : UserControl
{
    [ScriptableMember]
    public void StartUpload()
    {
        // ...
    }
} 

And, in Javascript:

function startUpload() {
    $find("<%= SilverlightUpload.ClientID %>")
        .get_element().content.uploadControl.StartUpload();
    return false;
}

So, I take a look on that HtmlPage.RegisterScriptableObject call and just expose types marked as [ScriptableType]