C#获取进程的主窗口句柄的实现方法

通过调用win32 api实现。

public class user32api
{
    private static hashtable processwnd = null;

    public delegate bool wndenumproc(intptr hwnd, uint lparam);

    static user32api()
    {
        if (processwnd == null)
        {
            processwnd = new hashtable();
        }
    }

    [dllimport("user32.dll", entrypoint = "enumwindows", setlasterror = true)]
    public static extern bool enumwindows(wndenumproc lpenumfunc, uint lparam);

    [dllimport("user32.dll", entrypoint = "getparent", setlasterror = true)]
    public static extern intptr getparent(intptr hwnd);

    [dllimport("user32.dll", entrypoint = "getwindowthreadprocessid")]
    public static extern uint getwindowthreadprocessid(intptr hwnd, ref uint lpdwprocessid);

    [dllimport("user32.dll", entrypoint = "iswindow")]
    public static extern bool iswindow(intptr hwnd);

    [dllimport("kernel32.dll", entrypoint = "setlasterror")]
    public static extern void setlasterror(uint dwerrcode);

    public static intptr getcurrentwindowhandle()
    {
        intptr ptrwnd = intptr.zero;
        uint uipid = (uint)process.getcurrentprocess().id;  // 当前进程 id
        object objwnd = processwnd[uipid];

        if (objwnd != null)
        {
            ptrwnd = (intptr)objwnd;
            if (ptrwnd != intptr.zero && iswindow(ptrwnd))  // 从缓存中获取句柄
            {
                return ptrwnd;
            }
            else
            {
                ptrwnd = intptr.zero;
            }
        }

        bool bresult = enumwindows(new wndenumproc(enumwindowsproc), uipid);
        // 枚举窗口返回 false 并且没有错误号时表明获取成功
        if (!bresult && marshal.getlastwin32error() == 0)
        {
            objwnd = processwnd[uipid];
            if (objwnd != null)
            {
                ptrwnd = (intptr)objwnd;
            }
        }

        return ptrwnd;
    }

    private static bool enumwindowsproc(intptr hwnd, uint lparam)
    {
        uint uipid = 0;

        if (getparent(hwnd) == intptr.zero)
        {
            getwindowthreadprocessid(hwnd, ref uipid);
            if (uipid == lparam)    // 找到进程对应的主窗口句柄
            {
                processwnd[uipid] = hwnd;   // 把句柄缓存起来
                setlasterror(0);    // 设置无错误
                return false;   // 返回 false 以终止枚举窗口
            }
        }

        return true;
    }
}

调用user32api.getcurrentwindowhandle()即可返回当前进程的主窗口句柄，如果获取失败则返回intptr.zero。

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