Setting focus to a textbox on load of Windows Phone 7 app

I have a TwoWay data-bound textbox inside my page. I want to do something pretty simple, but I can't for the life of me work out how to do it. When the page loads, I want to set the focus to the textbox if it doesn't have any text in it.

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
    if (tbSearch.Text == "")
     开发者_StackOverflow   tbSearch.Focus();
}

This doesn't work. It doesn't fail, it just doesn't do anything. Am I doing something strange wrong? I've also tried putting this in the constructor, to no avail.

Chris

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Does doing this from the pages Loaded event work for your requirements?

It will work from there.