如何從類庫檢查WPF窗口是否打開

Question

我從類庫打開WPF窗口。如何從類庫中檢查WPF窗口是否已經打開？到System.Windows.Application.Current.Windows任何引用產生此錯誤：

Object reference not set to an instance of an object

注：我從一個WPF項目，我改變了輸出類型類庫創建的類庫。

Answer 1

我試圖引用System.Windows但無法這樣做。

但是強制執行一個只有一個進程實例正在運行的規則是一個有趣的任務。在Win32上還有很多其他的編碼算法。它會檢測您的應用程序是否已經運行。如果檢測到，它會將該應用程序放到前臺（如果它被最小化）。

using System.Diagnostics; 
using System.Runtime.InteropServices; 
public class OnlyOneWindow 
{ 
    [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; 

    public OnlyOneWindow() 
    { 
     // 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. 
    } 
}