Single instance Application

I for the life of me cannot remember where I got this, so I'm not going to take credit for it, but this works

using System;
using System.Windows.Forms;
using System.Threading;
using System.Runtime.InteropServices;
using System.Diagnostics;


namespace Control_Center {
    static class Program {
        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool SetForegroundWindow(IntPtr hWnd);
        [DllImport("user32.dll")]
        public static extern bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);

        ///

        /// The main entry point for the application.
        ///

        [STAThread]
        static void Main() {
            bool createdNew = true;
            using (Mutex mutex = new Mutex(true, "Control Center", out createdNew)) {
                if (createdNew) {

                    Application.EnableVisualStyles();
                    Application.SetCompatibleTextRenderingDefault(false);
                    Application.Run(new frmCC());
                }
                else {
                    Process current = Process.GetCurrentProcess();
                    foreach (Process process in Process.GetProcessesByName(current.ProcessName)) {
                        if (process.Id != current.Id) {
                            SetForegroundWindow(process.MainWindowHandle);
                            ShowWindowAsync(process.MainWindowHandle,1);
                            break;
                        }
                    }   
                }
            }
        }
    }
}

Thank you Lizard for the support. You have heard the cliche about leading a horse to water. Sometimes people insist on doing things in an inferior manner.
 
I understand and agree that it is customary to activate an existing instance in situations such as that. If Patrick wanted that then we could solve that problem too.

Sorry to burst your bubble patrick but the Mutex is the only thing that will GUARANTEE a single instance  kirtans method will fail if you change the window title for whatever reason so his code may be short and sweet but it is NOT the correct way.

I appreciate everyones help, but love kirtans short and sweet code.

Absolutely correct Sam, the Mutex object is the correct object to use, but you should end the new instance and switch to an already running instance if one exists.

Absolutely correct Sam, the Mutex object is the correct object to use, but you should end the new instance and switch to an already running instance if one exists.

If you only need to detect a previous instance, then a Mutex is easy and effective. Note that you should place this code in the Program.cs file, not in the Form class. Put this code just before the line that says "Application.Run(new Form1());" or something such as that.

bool WasCreated;

const string MutexName = "Project_76468";

Mutex m = new Mutex(true, MutexName, out WasCreated);

if (!WasCreated)

{

	// MessageBox.Show("A previous instance exists");

	return;

}

Note that you need to also do the following after the "Application.Run(new Form1());":

GC.KeepAlive(m);

That line is not important for small programs, but always use it anyway.

Look at the right side of this page; do you see "Our recommended articles"? Do you see an article there about "Checking previous instance (single instance) of an C# windows application"? Does that help?
 
If that is not enough, then search the msdn for "single instance"; I hope that is enough.