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

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

It will work from there.