How to manually set and lose focus of a TextBox in WinRT Windows 8

Question

I have a Textbox and on the LostFocus event of it, I have a function called SaveWeight() to save the value based on few conditions. I need to programatically trigger that function.

For example, I have a OnClearButClicked function in which the the value in the textbox is cleared. So after it is cleared, I need to call the SaveWeight function. But since it is a LostFocus event I need to manually set the focus of the textbox to Unfocused which might hopefully trigger the SaveWeight().

private void OnClearButClicked(object sender, RoutedEventArgs e) {
    weightTBox.Text = "";
    weightTBox.Focus(Windows.UI.Xaml.FocusState.Unfocused);
}

But the weightTBox.Focus(Windows.UI.Xaml.FocusState.Unfocused); throws an ArgumentException. So is my approach wrong? Can I set the FocusState for an element and then trigger the event. Or some other thing I'm missing?

Answer 1

Why not just call the method, passing in null as the arguments?

SaveWeight(null, null);

It seems to me, setting focus in the UI is a huge violation of the separation of concerns in your code base.