在IE中从Javascript调用Silverlight代码

Question

I have a Silverlight application in an HTML page. The SL plugin is hosted in an "object" HTML tag. When the user closes the Web page, I want to call a function inside my Silverlight application. The code is something like this:

The (simplified) HTML code:

<div id="silverlightControlHost">
    <object id="MyApp" data="data:application/x-silverlight-2," type="application/x-silverlight-2" width="100%" height="100%">
        <param name="source" value="ClientBin/MyApp.xap" />
        ...
        </object><iframe id="_sl_historyFrame"></iframe></div>

The Javascript code:

<script type="text/javascript">
    window.onbeforeunload = confirmExit;

    function confirmExit()
    {
        var control = document.getElementById("MyApp");
        var message = control.content.BrowserIntegration.MyAppFunction();

        if (message)
        {
            return message;
        }
    }
</script>

It used to work and it doesn't work anymore, at least in Internet Explorer 8. The content property of the HTML object (control.content) is undefined. Strange. Has there been a change recently for this property? I am pretty sure that it worked 2 months ago, and that it has worked well for a long time before that. The Web site is in my trusted sites and I haven't found a setting in IE that I have changed since then (there could be one or two but, scanning the list, I haven't found anything).

When I make a test with the "onLoad" event of the HTML object, the content is already undefined.

I don't know if the anomaly is the fact that it worked before or that it doesn't work now. But if somebody can tell me how to make it work now, it will make my day.

Answer 1

I create some wizard for calling Silverlight code from IE:

1)Need identify a silverlight control: add "id" tag:

<object data="data:application/x-silverlight-2," type="application/x-silverlight-2"
            width="100%" height="100%" id="_sl_facebookapp">

2) Need register scriptable object from silverlight code:

HtmlPage.RegisterScriptableObject("FBSHandler", this);

3) Mark needed silverlight method as ScriptableMember:

[ScriptableMember]
        public void FBAuthorized(string authKey){}

4) You should use registered scriptable object for calling Silverlight method:

var silverlightCtrlId = '_sl_facebookapp';

function handleStatusResponse(response) {
    var control = document.getElementById(silverlightCtrlId);    
        var accessToken = response.authResponse.accessToken;
        if (control != null) {
            control.Content.FBSHandler.FBAuthorized(accessToken);
        }
    }
}

It works fine. Hope it will help you.

Answer 2

These operations did not solve my problem:

• Detecting and removing viruses
• Lowering the security level in IE8
• Reinstalling Internet Explorer 8
• Reinstalling the Silverlight component

This is what solved my problem:

• Reinstalling the Silverlight Developer runtime

Note: I use MS Visual Studio 2010 for .NET development

Answer 3

I think this is a timing issue. Your code to access the Content element may be executing before the Silverlight Component is entirely loaded.

I had the exact same issue and resolved it by using Javascript Timer till the element was completely loaded. Interestingly the issue was only with IE and none of the other browsers.