I'm trying to call a function in a Silverlight 4 component to open a file dialog and upload a file to the server. Everything works well within Silverlight but I'd like to call the component from JavaScript. So I call the button click handler from a C#-function which is [ScriptableMember]. I get the following error when calling the function:

System.Security.SecurityException: Dialogs must be user-initiated. 
at System.Windows.Browser.ManagedObjectInfo.Invoke(ManagedObject obj, InvokeType
invokeType, String memberName, ScriptParam[] args) at
System.Windows.Hosting.ManagedHost.InvokeScriptableMember(IntPtr pHandle, Int32 nMemberID,
Int32 nInvokeType, Int32 nArgCount, ScriptParam[] pArgs, ScriptParam& pResult,
ExceptionInfo& pExcepInfo)

I based my code on the tutorial by Tim Heuer that can be found here: http://www.silverlight.net/learn/videos/silverlight-videos/openfiledialog-and-file-upload/

I understand why the error is thrown, sort of, the 'click' from the user is done in JavaScript and probably is not going through to Silverlight. For Silverlight this is merely a function call.

Is this new policy from Silverlight 4? Is it still possible to only use Silverlight behind to screens to upload a file? Any help is appreciated.