只能打开一个实例
View Code
1 using System;
2 using System.Windows.Forms;
3 using System.Runtime.InteropServices;
4 using System.Threading;
5
6
7 namespace OneInstanceOnlyMethodOne
8 {
9 static class Program
10 {
11
12 #region DllImportAttribute
13
14 [DllImport("user32.dll", CharSet = CharSet.Unicode)]
15 static extern IntPtr FindWindow(string className, string windowText);
16
17 const int SW_HIDE = 0;
18 const int SW_RESTORE = 1;
19 const int SW_MAXIMIZE = 2;
20 const int SW_MINIMIZE = 3;
21 const int SW_SHOW = 4;
22 const int SW_SHOWDEFAULT = 5;
23
24 /// <summary>
25 /// 该函数设置指定窗口的显示状态。
26 /// </summary>
27 /// <param name="handle"></param>
28 /// <param name="flags"></param>
29 /// <returns></returns>
30 [DllImport("user32.dll", CharSet = CharSet.Unicode)]
31 static extern bool ShowWindow(IntPtr handle, int flags);
32
33 /// <summary>
34 /// 该函数将创建指定窗口的线程设置到前台，并且激活该窗口。
35 /// 键盘输入转向该窗口，并为用户改各种可视的记号。
36 /// 系统给创建前台窗口的线程分配的权限稍高于其他线程。
37 /// </summary>
38 /// <param name="handle"></param>
39 /// <returns></returns>
40 [DllImport("user32.dll", CharSet = CharSet.Unicode)]
41 static extern bool SetForegroundWindow(IntPtr handle);
42 #endregion
43
44 /// <summary>
45 /// 应用程序的主入口点。
46 /// </summary>
47 [STAThread]
48 static void Main()
49 {
50 bool isCreated; // 互斥体名称须唯一。
51 using (Mutex newMutex = new Mutex(true, "_OneInstanceOnly_", out isCreated))
52 {
53 if (isCreated)
54 {
55 Application.CurrentCulture = System.Globalization.CultureInfo.InvariantCulture;
56 Application.EnableVisualStyles();
57 Application.SetCompatibleTextRenderingDefault(false);
58 Application.Run(new MethodOneMainForm());
59 newMutex.ReleaseMutex(); // 释放互斥体的所属权。
60 }
61 else
62 {
63 string text = string.Format("“{0}”应用程序已经运行。", AppDomain.CurrentDomain.FriendlyName);
64 MessageBox.Show(text, "系统提示！", MessageBoxButtons.OK, MessageBoxIcon.Warning);
65
66 //查找之前打开的实例
67 IntPtr handle = FindWindow(null, "MethodOneMainForm");
68 if (handle != IntPtr.Zero)
69 {
70 //ShowWindow(handle, 1);
71 ShowWindow(handle, SW_RESTORE);
72 SetForegroundWindow(handle);
73 }
74 }
75 }
76 }
77 }
78 }
还有另外一种方法：
View Code
1 using System;
2 using System.Runtime.InteropServices;
3 using System.Windows.Forms;
4 using System.Diagnostics;
5
6 namespace OneInstanceOnlyMethodTwo
7 {
8 static class Program
9 {
10 [DllImport("user32.dll", EntryPoint = "SetForegroundWindow")]
11 public static extern int SetForegroundWindow(IntPtr hwnd);
12 [DllImport("user32.dll", EntryPoint = "SendMessage")]
13 public static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);
14 public const int WM_SYSCOMMAND = 0x112;
15 public const int SC_RESTORE = 0xF120;
16
17
18
19 /// <summary>
20 /// 应用程序的主入口点。
21 /// </summary>
22 [STAThread]
23 static void Main()
24 {
25
26 Process cur = Process.GetCurrentProcess();
27 foreach (Process p in Process.GetProcesses())
28 {
29 if (p.Id == cur.Id)
30 continue;
31 if (p.ProcessName == cur.ProcessName)
32 {
33 string text = string.Format("“{0}”已经运行。", AppDomain.CurrentDomain.FriendlyName);
34 MessageBox.Show(text, "系统提示！", MessageBoxButtons.OK, MessageBoxIcon.Warning);
35
36 SetForegroundWindow(p.MainWindowHandle);
37 SendMessage(p.MainWindowHandle, WM_SYSCOMMAND, SC_RESTORE, 0);
38 return;
39 }
40 }
41 Application.EnableVisualStyles();
42 Application.SetCompatibleTextRenderingDefault(false);
43 Application.Run(new MethodTwoMainForm());
44 }
45 }
46 }
