Ensure that only one instance of the application is running

[C #]

Public static Process RunningInstance ()

{

Process current = Process. GetCurrentProcess ();

Process [] processes = Process. GetProcessesByName (current. ProcessName );

// Loop through the running processes in with the same name

Foreach (Process process in processes)

{

// Ignore the current process

If (process. Id! = Current. Id)

{

// Make sure that the process is running from the exe file.

If (Assembly. GetExecutingAssembly (). Location. Replace ("/", "//") = current. MainModule. FileName)

{

// Return the other process instance.

Return process;

}

}

}

// No other instance was found, return null.

Return null;

}

[VB. NET]

Public Shared Function RunningInstance () As Process

Dim current As Process = Process. GetCurrentProcess ()

Dim processes As Process () = Process. GetProcessesByName (current. ProcessName)

'Loop through the running processes in with the same name

Dim process As Process

For Each process In processes

'Ignore the current process

If process. Id <> current. Id Then

'Make sure that the process is running from the exe file.

If [Assembly]. GetExecutingAssembly (). Location. Replace ("/", "/") = current. MainModule. FileName Then

'Return the other process instance.

Return process

End If

End If

Next process

'No other instance was found, return null.

Return Nothing

End Function 'runninginstance

If an existing form instance is detected, the instance is displayed for reference:

[STAThread] Static void Main () { // Get the running instance. Process instance = RunningInstance (); If (instance = null) { // There isn' t another instance, show our form. Application. Run (new Form2 ()); } Else { // There is another instance of this process. HandleRunningInstance (instance ); } } Public static Process RunningInstance () { Process current = Process. GetCurrentProcess (); Process [] processes = Process. GetProcessesByName (current. ProcessName ); // Loop through the running processes in with the same name Foreach (Process process in processes) { // Ignore the current process If (process. Id! = Current. Id) { // Make sure that the process is running from the exe file. If (Assembly. GetExecutingAssembly (). Location. Replace ("/", "//") = current. MainModule. FileName) { // Return the other process instance. Return process; } } } // No other instance was found, return null. Return null; } Public static void HandleRunningInstance (Process instance) { // Make sure the window is not minimized or maximized ShowWindowAsync (instance. main1_whandle, WS_SHOWNORMAL ); // Set the real intance to foreground window SetForegroundWindow (instance. main1_whandle ); } [DllImport ("User32.dll")] Private static extern bool ShowWindowAsync (IntPtr hWnd, int cmdShow ); [DllImport ("User32.dll")] Private static extern bool SetForegroundWindow (IntPtr hWnd ); Private const int WS_SHOWNORMAL = 1

Source: http://blog.csdn.net/acewang/archive/2004/02/05/17627.aspx