CODE EXAMPLE FOR CSHARP

wpf numeric only textbox

<TextBox Name="NumberTextBox" PreviewTextInput="NumberValidationTextBox"/>

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using System.Text.RegularExpressions;
private void NumberValidationTextBox(object sender, TextCompositionEventArgs e)
{
    Regex regex = new Regex("[^0-9]+");
    e.Handled = regex.IsMatch(e.Text);
}