text box two decimal value

Question

C# visual studio 2015. I have a text box. I do not want to write more than two decimal value. I have tried like this:

private void txtAPenPension_TextChanged(object sender, EventArgs e)

{

if (System.Text.RegularExpressions.Regex.IsMatch(txtAPenPension.Text, " ^ [0-9]"))

{

txtAPenPension.Text = "";

}

}