Restricting characters in a TextBox

Question

I'm building a form in a C# WinRT app, and I'd like to restrict the characters in one of the TextBox components to numerals only. (This TextBox would be for a user to enter a year into.)

I've searched for a while, but haven't been able to figure this one out without setting up an event listener on the TextChanged event, and inspecting the text property on every key press. Is there a way to simply say that a user can only enter specific characters into a TextBox?

Answer 1

The simplest thing that could possibly work is to bind to the OnTextChanged event and modify the text according to your rules.

    <TextBox x:Name="TheText" TextChanged="OnTextChanged" MaxLength="4"/>

    private void OnTextChanged(object sender, TextChangedEventArgs e)
    {
        if (TheText.Text.Length == 0) return;

        var text = TheText.Text;

        int result;
        var isValid = int.TryParse(text, out result);
        if (isValid) return;

        TheText.Text = text.Remove(text.Length - 1);
        TheText.SelectionStart = text.Length;
    }

However, I'd shy away from this approach since the mantra of Metro is touch first UI and you can easy do it in a touch first manner with a FlipView control.

Answer 2

Try setting TextBox.InputScope property to InputScopeNameValue.Number, as mentioned in Guidelines and checklist for text input in MSDN.