c#怎么让textBox只能接收数字

private bool IsValid(string input)
        {
            Regex regex = new Regex("[0-9]");
            return regex.IsMatch(input);
        }
private void textBox_Leave(object sender, EventArgs e)
        {
            if (textBox.Text != "")
            {
                IsValid(textBox.Text);
                if (IsValid(textBox.Text) == false)
                    MessageBox.Show("请输入数字");
            }
        }