如何在 C# 中获取连接到 PC 的显示器数量？

Question

我需要检测物理连接到计算机的显示器数量（以确定屏幕配置是否处于单一、扩展、重复模式）。 System.Windows.Forms.Screen.AllScreens.Length 和 System.Windows.Forms.SystemInformation.MonitorCount 都返回虚拟屏幕（桌面）的计数。

所以，如果有 2 个以上的显示器连接到 PC，我可以使用此值在复制/扩展模式之间做出决定，但我无法决定是否只有一个物理显示器连接到 PC，因此屏幕配置是在单屏模式下。

Answer 1

基于 Xanatos 的回答，我创建了简单的帮助类来检测屏幕配置：

using System;
using System.Management;
using System.Windows.Forms;

public static class ScreensConfigurationDetector
{
    public static ScreensConfiguration GetConfiguration()
    {
        int physicalMonitors = GetActiveMonitors();
        int virtualMonitors = Screen.AllScreens.Length;

        if (physicalMonitors == 1)
        {
            return ScreensConfiguration.Single;
        }

        return physicalMonitors == virtualMonitors 
            ? ScreensConfiguration.Extended 
            : ScreensConfiguration.DuplicateOrShowOnlyOne;
    }

    private static int GetActiveMonitors()
    {
        int counter = 0;
        ManagementObjectSearcher monitorObjectSearch = new ManagementObjectSearcher("SELECT * FROM Win32_DesktopMonitor");
        foreach (ManagementObject Monitor in monitorObjectSearch.Get())
        {
            try
            {
                if ((UInt16)Monitor["Availability"] == 3)
                {
                    counter++;
                }
            }
            catch (Exception)
            {
                continue;
            }

        }
        return counter;
    }
}

public enum ScreensConfiguration
{
    Single,
    Extended,
    DuplicateOrShowOnlyOne
}

Answer 2

尝试以下方法：

    System.Management.ManagementObjectSearcher monitorObjectSearch = new System.Management.ManagementObjectSearcher("SELECT * FROM Win32_DesktopMonitor");
    int Counter = monitorObjectSearch.Get().Count;

找到以下问题的答案：

WMI Get All Monitors Not Returning All Monitors

更新

尝试以下检测到拔出显示器的功能：

    private int GetActiveMonitors()
    {
        int Counter = 0;
        System.Management.ManagementObjectSearcher monitorObjectSearch = new System.Management.ManagementObjectSearcher("SELECT * FROM Win32_DesktopMonitor");
        foreach (ManagementObject Monitor in monitorObjectSearch.Get())
        {
            UInt16 Status = 0;
            try
            {
                Status = (UInt16)Monitor["Availability"];
            }
            catch (Exception ex)
            {
                //Error handling if you want to
                continue;
            }
            if (Status == 3)
                Counter++;

        }
        return Counter;
    }

以下是状态列表：https://msdn.microsoft.com/en-us/library/aa394122%28v=vs.85%29.aspx

也许您还需要增加其他状态码的计数器。查看链接了解更多信息。

Answer 3

我发现在 WPF 中获取监视器计数的最可靠方法是侦听 WM_DISPLAYCHANGE 以了解 mionitor 何时连接和断开连接，然后使用 EnumDisplayMonitors 获取监视器计数。这是代码。

挂钩到 WndProc 以获取 WM_DISPLAYCHANGE 消息。

public partial class MainWindow : IDisposable
{
...
        protected override void OnSourceInitialized(EventArgs e)
        {
            base.OnSourceInitialized(e);
            HwndSource source = PresentationSource.FromVisual(this) as HwndSource;
            source.AddHook(WndProc);
        }

        private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            if (msg == WM_DISPLAYCHANGE)
            {
                int lparamInt = lParam.ToInt32();

                uint width = (uint)(lparamInt & 0xffff);
                uint height = (uint)(lparamInt >> 16);

                int monCount = ScreenInformation.GetMonitorCount();
                int winFormsMonCount = System.Windows.Forms.Screen.AllScreens.Length;

                _viewModel.MonitorCountChanged(monCount);
            }

            return IntPtr.Zero;
        }

获取展示次数

public class ScreenInformation
{
    [StructLayout(LayoutKind.Sequential)]
    private struct ScreenRect
    {
        public int left;
        public int top;
        public int right;
        public int bottom;
    }

    [DllImport("user32")]
    private static extern bool EnumDisplayMonitors(IntPtr hdc, IntPtr lpRect, MonitorEnumProc callback, int dwData);

    private delegate bool MonitorEnumProc(IntPtr hDesktop, IntPtr hdc, ref ScreenRect pRect, int dwData);

    public static int GetMonitorCount()
    {
        int monCount = 0;
        MonitorEnumProc callback = (IntPtr hDesktop, IntPtr hdc, ref ScreenRect prect, int d) => ++monCount > 0;

        if (EnumDisplayMonitors(IntPtr.Zero, IntPtr.Zero, callback, 0))
            Console.WriteLine("You have {0} monitors", monCount);
        else
            Console.WriteLine("An error occured while enumerating monitors");

        return monCount;
    }
}

Answer 4

“SELECT * FROM Win32_DesktopMonitor”查询在 Vista 之后可能无法正常工作。我花了几个小时寻找解决方案，但没有一个能够在 Windows 7 和更高版本中正确处理这个问题。基于Dominik's answer；

ManagementObjectSearcher searcher = new ManagementObjectSearcher("root\\CIMV2", "SELECT * FROM Win32_PnPEntity where service=\"monitor\"");
int numberOfMonitors = searcher.Get().Count;

将返回物理监视器的计数。有了这个改变，他的助手类也对我有用。