How to use C# string Format

using System;
using System.Windows.Forms;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            double dNum = 0;
            dNum = 32.123456789;
            MessageBox.Show("Formated String " + string.Format("{0:n4}", dNum)); 
        }
    }
}

When you run this C# source code you will get "Formated String 32.1234"