一个Win32 API实例类（代码收集）

　　最近看到别人代码中一个很好的功能类，该类是一个Win32 API实例类，该类功能包括：同一程序禁止启动多次；获取任意窗体；恢复窗体状态；设置窗体焦点等。

该类很实用，与大家分享一下：

　　

1 /// Summary description for ProcessUtils.
2 public static class ProcessUtils
3 {
4 private static Mutex mutex = null;
5
6 /// Determine if the current process is already running
7 public static bool ThisProcessIsAlreadyRunning()
8 {
9 // Only want to call this method once, at startup.
10 Debug.Assert(mutex == null);
11
12 // createdNew needs to be false in .Net 2.0, otherwise, if another instance of
13 // this program is running, the Mutex constructor will block, and then throw
14 // an exception if the other instance is shut down.
15 bool createdNew = false;
16
17 mutex = new Mutex(false, Application.ProductName, out createdNew);
18
19 Debug.Assert(mutex != null);
20
21 return !createdNew;
22 }
23
24 [DllImport("user32.dll", SetLastError = true)]
25 static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
26
27 [DllImport("user32.dll")]
28 [return: MarshalAs(UnmanagedType.Bool)]
29 static extern bool SetForegroundWindow(IntPtr hWnd);
30
31 [DllImport("user32.dll")]
32 static extern bool IsIconic(IntPtr hWnd);
33
34 [DllImport("user32.dll")]
35 static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
36
37 const int SW_RESTORE = 9;
38
39 [DllImport("user32.dll")]
40 static extern IntPtr GetLastActivePopup(IntPtr hWnd);
41
42 [DllImport("user32.dll")]
43 static extern bool IsWindowEnabled(IntPtr hWnd);
44
45 /// Set focus to the previous instance of the specified program.
46 public static void SetFocusToPreviousInstance(string windowCaption)
47 {
48 // Look for previous instance of this program.
49 IntPtr hWnd = FindWindow(null, windowCaption);
50
51 // If a previous instance of this program was found...
52 if (hWnd != null)
53 {
54 // Is it displaying a popup window?
55 IntPtr hPopupWnd = GetLastActivePopup(hWnd);
56
57 // If so, set focus to the popup window. Otherwise set focus
58 // to the program's main window.
59 if (hPopupWnd != null && IsWindowEnabled(hPopupWnd))
60 {
61 hWnd = hPopupWnd;
62 }
63
64 SetForegroundWindow(hWnd);
65
66 // If program is minimized, restore it.
67 if (IsIconic(hWnd))
68 {
69 ShowWindow(hWnd, SW_RESTORE);
70 }
71 }
72 }
73 }