C#判断是程序是否已经打开，如果打开就前置显示

[DllImport("user32.dll")]
private static extern bool SetForegroundWindow(IntPtr hWnd);
[DllImport("user32.dll")]
private static extern bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);
[DllImport("user32.dll")]
private static extern bool IsIconic(IntPtr hWnd);
private const int SW_RESTORE = 9;

/// <summary>
/// 判断是程序是否已经打开，如果打开就前置显示
/// </summary>
public static void RaiseOtherProcess()
{
Process proc = Process.GetCurrentProcess();
Process.GetProcesses();
foreach (Process otherProc in Process.GetProcessesByName(proc.ProcessName))
{
//ignore "this" process
if (proc.Id != otherProc.Id)
{
// Found a "same named process".
// Assume it is the one we want brought to the foreground.
// Use the Win32 API to bring it to the foreground.
IntPtr hWnd = otherProc.MainWindowHandle;
if (IsIconic(hWnd))
{
ShowWindowAsync(hWnd, 9);
}
SetForegroundWindow(hWnd);
break;
}
}
}

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
class AppMain
{
    [DllImport("user32.dll")] private static extern
        bool SetForegroundWindow(IntPtr hWnd);
    [DllImport("user32.dll")] private static extern
        bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);
    [DllImport("user32.dll")] private static extern
        bool IsIconic(IntPtr hWnd);

    private const int SW_HIDE = 0;
    private const int SW_SHOWNORMAL = 1;
    private const int SW_SHOWMINIMIZED = 2;
    private const int SW_SHOWMAXIMIZED = 3;
    private const int SW_SHOWNOACTIVATE = 4;
    private const int SW_RESTORE = 9;
    private const int SW_SHOWDEFAULT = 10;

    static void Main()
    {
        // get the name of our process
        string proc=Process.GetCurrentProcess().ProcessName;
        // get the list of all processes by that name
        Process[] processes=Process.GetProcessesByName(proc);
        // if there is more than one process...
        if (processes.Length > 1)
        {
            // Assume there is our process, which we will terminate, 
            // and the other process, which we want to bring to the 
            // foreground. This assumes there are only two processes 
            // in the processes array, and we need to find out which 
            // one is NOT us.

            // get our process
            Process p=Process.GetCurrentProcess();
            int n=0;        // assume the other process is at index 0
            // if this process id is OUR process ID...
            if (processes[0].Id==p.Id)
            {
                // then the other process is at index 1
                n=1;
            }
            // get the window handle
            IntPtr hWnd=processes[n].MainWindowHandle;
            // if iconic, we need to restore the window
            if (IsIconic(hWnd))
            {
                ShowWindowAsync(hWnd, SW_RESTORE);
            }
            // bring it to the foreground
            SetForegroundWindow(hWnd);
            // exit our process
            return;
        }
        // ... continue with your application initialization here.
    }
}

//该片段来自于http://outofmemory.cn

防止程序运行多个实例的方法有多种,如:通过使用互斥量和进程名等.而我想要实现的是:在程序运行多个实例时激活的是第一个实例,使其获得焦点,并在前端显示.

主要用到两个API 函数:

• ShowWindowAsync 该函数设置由不同线程产生的窗口的显示状态。
• SetForegroundWindow 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。键盘输入转向该窗口，并为用户改各种可视的记号。系统给创建前台窗口的线程分配的权限稍高于其他线程。

代码如下：

引用以下命名空间：
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Reflection;



 1 static class Program 
    { 
        /// <summary> 
        /// 该函数设置由不同线程产生的窗口的显示状态。 
        /// </summary> 
        /// <param name="hWnd">窗口句柄</param> 
        /// <param name="cmdShow">指定窗口如何显示。查看允许值列表，请查阅ShowWlndow函数的说明部分。</param> 
        /// <returns>如果函数原来可见，返回值为非零；如果函数原来被隐藏，返回值为零。</returns> 
        [DllImport("User32.dll")] 
        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow); 
        /// <summary> 
        /// 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。键盘输入转向该窗口，并为用户改各种可视的记号。系统给创建前台窗口的线程分配的权限稍高于其他线程。 
        /// </summary> 
        /// <param name="hWnd">将被激活并被调入前台的窗口句柄。</param> 
        /// <returns>如果窗口设入了前台，返回值为非零；如果窗口未被设入前台，返回值为零。</returns> 
        [DllImport("User32.dll")] 
        private static extern bool SetForegroundWindow(IntPtr hWnd); 
        private const int WS_SHOWNORMAL = 1;

        /// <summary> 
        /// 应用程序的主入口点。 
        /// </summary> 
        [STAThread] 
        static void Main() 
        { 
            Application.EnableVisualStyles(); 
            Application.SetCompatibleTextRenderingDefault(false); 
            Process instance = RunningInstance(); 
            if (instance == null) 
            { 
                Form1 frm = new Form1(); 
                Application.Run(new Form1()); 
            } 
            else 
            { 
                HandleRunningInstance(instance); 
            }

        } 
        /// <summary> 
        /// 获取正在运行的实例，没有运行的实例返回null; 
        /// </summary> 
        public static Process RunningInstance() 
        { 
            Process current = Process.GetCurrentProcess(); 
            Process[] processes = Process.GetProcessesByName(current.ProcessName); 
            foreach (Process process in processes) 
            { 
                if (process.Id != current.Id) 
                { 
                    if (Assembly.GetExecutingAssembly().Location.Replace("/", "\\") == current.MainModule.FileName) 
                    { 
                        return process; 
                    } 
                } 
            } 
            return null; 
        }

        /// <summary> 
        /// 显示已运行的程序。 
        /// </summary> 
        public static void HandleRunningInstance(Process instance) 
        { 
            ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL); //显示，可以注释掉 
            SetForegroundWindow(instance.MainWindowHandle);            //放到前端 
        } 
    }

 

我们基本上可以使用Windows API函数ShowWindowAsync方法来正常化/最大化/最小化另一应用程序。
请参阅下面的代码示例片段：
private const int SW_SHOWNORMAL = 1;
private const int SW_SHOWMINIMIZED = 2;
private const int SW_SHOWMAXIMIZED = 3;

[DllImport("user32.dll")]
private static extern bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);
private void button1_Click(object sender, EventArgs e)
{
    // 返回写字板程序的句柄
    IntPtr hWnd = FindWindow("Notepad", "Untitled - Notepad");
    if (!hWnd.Equals(IntPtr.Zero))
    {
        // SW_SHOWMAXIMIZED最大化窗口
        // SW_SHOWMINIMIZED 最小化窗口
        // SW_SHOWNORMAL 是窗口正常大小
        ShowWindowAsync(hWnd, SW_SHOWMAXIMIZED);
    }
}

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