Only one form is started. If it is started again, the form is activated.

1 Using System;
2 Using System. Collections. Generic;
3 Using System. Windows. forms;
4 Using System. diagnostics;
5 Using System. runtime. interopservices;
6
7 Namespace Windowsapplication2
8 {
9 Static Class Program
10 {
11 /// <Summary>
12///The main entry point of the application.
13/// </Summary>
14
15 [Dllimport ( " User32.dll " )]
16 Private Static Extern Bool Showwindowasync (intptr hwnd, Int Cmdshow );
17 [Dllimport ( " User32.dll " )]
18 Private Static Extern Bool Setforegroundwindow (intptr hwnd );
19 Private Const Int Ws_shownormal = 1 ;
20
21 [Stathread]
22 Static Void Main ()
23 {
24 // Get the running routine
25 Process instance = Runninginstance ();
26 If (Instance = Null )
27 {
28 // If there are no other routines, create a new form.
29 Application. enablevisualstyles ();
30 Application. setcompatibletextrenderingdefault ( False );
31 Application. Run ( New Form1 ());
32 }
33 Else
34 {
35//Process the detected routine
36Handlerunninginstance (instance );
37}
38 }
39 /// <Summary>
40///Get the running process
41/// </Summary>
42/// <Returns> </returns>
43 Public Static Process runninginstance ()
44 {
45 Process current = Process. getcurrentprocess ();
46 Process [] Processes = Process. getprocessesbyname (current. processname );
47
48 // Traversing a process with the same name running
49 Foreach (Process In Processes)
50 {
51 // Ignore existing processes
52 If (Process. ID ! = Current. ID)
53 {
54 // Make sure the process runs from the EXE file
55 If (Process. mainmodule. filename = Current. mainmodule. filename)
56 {< br> 57 // return to another process instance
58 return process;
59 }
60 }
61 }
62 // If no other process exists, null is returned.
63 Return Null ;
64 }
65 /// <Summary>
66 /// Processes a running process, that is, activating it.
67 /// </Summary>
68 /// <Param name = "instance"> Process to be processed </Param>
69 Public Static Void Handlerunninginstance (process instance)
70 {
71 // Ensure that the window is not minimized or maximized
72 Showwindowasync (instance. main1_whandle, ws_shownormal );
73 // Set the actual process to foreground window
74 Setforegroundwindow (instance. main1_whandle );
75 }
76 }
77 }