How to use C# string Concat

using System;
using System.Windows.Forms;

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

        private void button1_Click(object sender, EventArgs e)
        {
            string str1 = null;
            string str2 = null;

            str1 = "Concat() ";
            str2 = "Test";
            MessageBox.Show(string.Concat(str1, str2)); 
        }
    }
}

When you run this C# source code you will get "Concat() Test " in message box.