Home > Posts > Can’t step-through Silverlight file dialogs with Visual Studio debugger

Can’t step-through Silverlight file dialogs with Visual Studio debugger

While stepping through “ShowDialog()” method of OpenFileDialog with Visual Studio 2010 debugger, at the Silverlight code pictured below (for loading a ClipFlair window’s stored options), I got a “Dialogs must be user-initiated” exception. Same behaviour will be shown with SaveFileDialog too, every time you try to step through the “ShowDialog()” method.

This is because of Silverlight’s security model, which doesn’t allow source code to programmatically show a file dialog when an app is running in its default security sandbox (app is not signed with certificate and user hasn’t given consent for it to run in elevated rights mode), unless that code is called from an event handler that handles some user action on the UI (e.g. some button has been clicked by the user).

Obviously, when stepping through with the debugger it loses the user-initiated-action context somehow and considers the debugger as the initiator of the action, thus not allowing the file dialog to be shown when you try to step-through the “ShowDialog()” method of OpenFileDialog or SaveFileDialog.

The only solution I can suggest is to put a breakpoint right after the “ShowDialog()” returns (e.g. at “using” statement in the code below). If you place a breakpoint at any source code row above or at the “ShowDialog” inside the event handler method (“btnLoad_Click” in the code below) it will fail when the debugger tries to go through the “ShowDialog” method, even if you press “Run” after that breakpoint fires to continue.

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