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Asked: 2026-06-01T03:15:27+00:00

I have a Silverlight control with a method named DoSomething() decorated with the <ScriptableMember()>

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I have a Silverlight control with a method named DoSomething() decorated with the <ScriptableMember()> attribute. I then call this method successfully from JavaScript and proved by a little message box that apprears from the SL side that says “Method Called!”.

Point is all that works. The problem I am having is that prior to calling this method I build up an ObservableCollection on the Silverlight control containing 1..n FileInfo objects. This works fine too and builds up as I add files to it. Each time I add a file, a messagebox tells me the count from Silverlight (i.e. “Count = 2”).

Now the problem: when I call the method DoSomething() from JS and access that ObservableCollection the count = 0! To see what is going on I placed a message in the Silverlight control’s constructor to see if it gets entered upon being called from JS, and indeed it does and appears to recreate the control.

If this is the case it kind of makes sense that my ObservableCollection has a count = 0 because it is not the same control instance where I built up the FileInfo collection.

So how in the world do I preserve the collection, and why would simply calling a method exposed to JS from Silverlight, recreate the control and not allow me to access it’s given state? I don’t want a new control, I need to manipulate it as-is. Or am I off base and doing something else wrong to cause this beahvior?

Thoughts? Thanks!

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1 Answer

  1. Editorial Team

    It turns out the instance registered was the culprit. The MSDN examples show registering a new instance of the type, but in my case I needed the actual instance of the Page Control itself which solved the problem.

    So at the completion of my page’s initialization, I could register the current page’s instance like below:

    HtmlPage.RegisterScriptableObject("SLControl", Me)

    This allowed me from JS to access the control in it’s current state which included all objects in the ObservableCollection as required. I blogged about this topic with code examples and the article below expands on this situation:

    Get A Silverlight Control’s Current Instance For Communicating Via The HTML Bridge:
    http://allen-conway-dotnet.blogspot.com/2012/03/get-silverlight-controls-current.html

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