Find sum of digits of a number

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Find_sum_of_digits_of_a_number
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
int sum = 0;
int num1 = int.Parse(textBox1.Text);
int num2 = num1;
while (num2 > 0)
{
sum += (num2 % 10);
num2 /= 10;
}
MessageBox.Show("Total sum of the digits is:"+sum.ToString());
}
}
}