How to allow only 10 digits using regex?

Allow only 10 digits as input & validate it using regex...

private void button1_Click(object sender, EventArgs e)
{
           System.Text.RegularExpressions.Regex regex = new System.Text.RegularExpressions.Regex(@"^[0-9]{10}$");
            if (regex.IsMatch(textBox1.Text))
            {
                 MessageBox.Show("Value is correct.");
            }
            else
            {
                 MessageBox.Show("Value is not correct.");
            }
}