How to enter only digit in textbox using c# ?

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

namespace Enter_Digit_only_in_Textbox

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)

        {

                   

        }

        private void txtpass_TextChanged(object sender, EventArgs e)

        {

            if (System.Text.RegularExpressions.Regex.IsMatch(txtpass.Text, " ^ [0-9]"))// it is used regular expression for matching key

            {

                txtpass.Text = "";

            }

        }

        private void txtpass_KeyPress(object sender, KeyPressEventArgs e)

        {

            if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) && (e.KeyChar != '.'))

            {

                e.Handled = true;

            }

        }

    }

}