CODEWITHSUNDEEP
c#wpftextbox
Dan Luxford
Dan Luxford

Reputation: 1

Textbox Content string, but want only numbers when entering characters in textbox

I am very new to programming and mainly am doing it as a hobby, but I have made a few small executable programs to help me with my work (little industry specific calculators.

On to the question, I have a textbox with a content shown before focus, which I would like to keep, but also I would like to allow only numbers to be entered, is there any way of doing this.

Upvotes: 0

Views: 139

Answers (2)

Markus Palcer
Markus Palcer

Reputation: 31

If you want to avoid using code-behind, you can convert the above answer into a behavior by creating a class (e.g. DigitsOnlyBehavior) that contains an AttachedProperty. When the attached property is set, you register the handler which is defined and implemented in your behavior class.

One short example:

public static class MyBehavior
{
  public static readonly DependencyProperty AllowOnlyDigitsProperty = DependencyProperty.RegisterAttached(
    "AllowOnlyDigits", typeof(bool), typeof(MyBehavior), new PropertyMetadata(default(bool), OnAllowOnlyDigitsChanged));

  private static void OnAllowOnlyDigitsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
  {
    var textBox = d as TextBox;
    if (textBox == null) return;
    textBox.PreviewTextInput += PreviewTextBoxInput;
  }

  public static void SetAllowOnlyDigits(DependencyObject element, bool value)
  {
    element.SetValue(AllowOnlyDigitsProperty, value);
  }

  private static void PreviewTextBoxInput(object sender, TextCompositionEventArgs e)
  {
    var textbox = sender as TextBox;

    if (!char.IsDigit(e.Text, e.Text.Length - 1))
      e.Handled = true;
  }


  public static bool GetAllowOnlyDigits(DependencyObject element)
  {
    return (bool) element.GetValue(AllowOnlyDigitsProperty);
  }
}

As you can see the PreviewTextBoxInput function is mainly what the previous post suggests.

You can now "attach" that behavior in your XAML like this:

    <TextBox local:MyBehavior.AllowOnlyDigits="True" />

This solution is not fully complete, since it does not support changing the property (it will attach the handler each time the property changes, so it assumes you only set it once via XAML). But if you don't want to change this behavior during runtime, you're fine.

Upvotes: 0

Gabriel
Gabriel

Reputation: 411

Try adding PreviewTextInput event handler to your TextBox. 

textBox1.PreviewTextInput += new TextCompositionEventHandler(textBox1_PreviewTextInput);

In your event handler test if entered character is digit. 

private void textBox1_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
    if (!char.IsDigit(e.Text, e.Text.Length - 1))
        e.Handled = true;
}

Upvotes: 1

Related Questions