How to limit certain characters in a TextBox in WPF?

Question

WPF

How, for example, to make it possible to enter only numbers in the TextBox text field? Or vice versa, only letters. I was looking for information about this, I found a solution for WinForms. Tried like this option:

char number = e.KeyChar;
 
 if (!Char.IsDigit(number))
 {
    e.Handled = true;
 }

So is this one:

if (e.KeyChar <= 47 || e.KeyChar >= 58)
{
    e.Handled = true;
}

For WPF they didn't work

Answer 1

Should work, hang on the PreviewTextInput event and check not e.KeyChar, but e.Text
of type

public Window()
        {
            InitializeComponent();
            this.textBox.PreviewTextInput += new TextCompositionEventHandler(textBox_PreviewTextInput);
        }
 
        void textBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
        {
            if (!Char.IsDigit(e.Text,0)) e.Handled = true;
        }