Question

我正在从类库中打开一个WPF窗口。如果WPF窗口已经打开，如何从类库中检查？对System.Windows.Application.Current.Windows的任何引用都会产生此错误：

对象引用未设置为对象的实例

注意：我从WPF项目创建了类库，我将输出类型更改为类库。

Answer 1

我尝试引用 System.Windows ，但无法执行此操作。

但是强制执行只有一个进程实例正在运行的规则是一项有趣的任务。在Win32上还有许多其他方法可以编写算法。它会检测您的应用程序的实例是否已在运行。如果检测到，它将把该应用程序带到前台（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.
    }
}

如果打开WPF窗口，如何从类库中检查

1 个答案: