Activating a single application instance form

Question

In a C # Windows Forms application, I want to determine if another instance of the application is running. If so, activate the main form of the executable instance and exit this instance.

What is the best way to achieve this?

Answer 1

Scott Hanselman answers your question in detail.

Answer 2

Here is what I am doing now in the application's Program.cs file.

// Sets the window to be foreground [DllImport("User32")] private static extern int SetForegroundWindow(IntPtr hwnd); // Activate or minimize a window [DllImportAttribute("User32.DLL")] private static extern bool ShowWindow(IntPtr hWnd, int nCmdShow); private const int SW_RESTORE = 9; static void Main() { try { // If another instance is already running, activate it and exit Process currentProc = Process.GetCurrentProcess(); foreach (Process proc in Process.GetProcessesByName(currentProc.ProcessName)) { if (proc.Id != currentProc.Id) { ShowWindow(proc.MainWindowHandle, SW_RESTORE); SetForegroundWindow(proc.MainWindowHandle); return; // Exit application } } Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(new MainForm()); } catch (Exception ex) { } } 

Answer 3

You can use this detection and activate your instance after it:

  // Detect existing instances string processName = Process.GetCurrentProcess().ProcessName; Process[] instances = Process.GetProcessesByName(processName); if (instances.Length > 1) { MessageBox.Show("Only one running instance of application is allowed"); Process.GetCurrentProcess().Kill(); return; } // End of detection 

Answer 4

Aku, this is a good resource. I answered a question similar to this one some time ago. You can check my answer here . Although this was for WPF, you can use the same logic in WinForms.