C#判断Windows当前是否有全屏应用

新建一个 AppWrapper工具类，用来注册事件，获取窗口句柄。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace CombinationKeyRecord
{
    public class APIWrapper
    {
        [DllImport("SHELL32", CallingConvention = CallingConvention.StdCall)]
        public static extern uint SHAppBarMessage(int dwMessage, ref APPBARDATA pData);
        [DllImport("User32.dll", CharSet = CharSet.Auto)]
        public static extern int RegisterWindowMessage(string msg);
        //取得Shell窗口句柄函数 
        [DllImport("user32.dll")] 
        public static extern IntPtr GetShellWindow();
        //取得桌面窗口句柄函数 
        [DllImport("user32.dll")]
        public static extern IntPtr GetDesktopWindow();
        //取得前台窗口句柄函数 
        [DllImport("user32.dll")]
        public static extern IntPtr GetForegroundWindow();
    }
    [StructLayout(LayoutKind.Sequential)]
    public struct RECT
    {
        public int left;
        public int top;
        public int right;
        public int bottom;
    }
    [StructLayout(LayoutKind.Sequential)]
    public struct APPBARDATA
    {
        public int cbSize;
        public IntPtr hWnd;
        public int uCallbackMessage;
        public int uEdge;
        public RECT rc;
        public IntPtr lParam;
    }
    public enum ABMsg : int
    {
        ABM_NEW = 0,
        ABM_REMOVE,
        ABM_QUERYPOS,
        ABM_SETPOS,
        ABM_GETSTATE,
        ABM_GETTASKBARPOS,
        ABM_ACTIVATE,
        ABM_GETAUTOHIDEBAR,
        ABM_SETAUTOHIDEBAR,
        ABM_WINDOWPOSCHANGED,
        ABM_SETSTATE
    }
    public enum ABNotify : int
    {
        ABN_STATECHANGE = 0,
        ABN_POSCHANGED,
        ABN_FULLSCREENAPP,
        ABN_WINDOWARRANGE
    }
    public enum ABEdge : int
    {
        ABE_LEFT = 0,
        ABE_TOP,
        ABE_RIGHT,
        ABE_BOTTOM
    }
}

在Form类中添加这些方法和属性

　　　　 Boolean RunningFullScreenApp = false;
        private IntPtr desktopHandle;
        private IntPtr shellHandle;
        int uCallBackMsg;

        private void RegisterAppBar(bool registered)
        {
            APPBARDATA abd = new APPBARDATA();
            abd.cbSize = Marshal.SizeOf(abd);
            abd.hWnd = this.Handle;

            desktopHandle = APIWrapper.GetDesktopWindow();
            shellHandle = APIWrapper.GetShellWindow();
            if (!registered)
            {
                //register
                uCallBackMsg = APIWrapper.RegisterWindowMessage("APPBARMSG_CSDN_HELPER");
                abd.uCallbackMessage = uCallBackMsg;
                uint ret = APIWrapper.SHAppBarMessage((int)ABMsg.ABM_NEW, ref abd);
            }
            else
            {
                APIWrapper.SHAppBarMessage((int)ABMsg.ABM_REMOVE, ref abd);
            }
        }

        
        //重载窗口消息处理函数
        protected override void WndProc(ref System.Windows.Forms.Message m)
        {
            if (m.Msg == uCallBackMsg)
            {
                switch (m.WParam.ToInt32())
                {
                    case (int)ABNotify.ABN_FULLSCREENAPP:
                        {
                            IntPtr hWnd = APIWrapper.GetForegroundWindow();
                            //判断当前全屏的应用是否是桌面
                            if(hWnd.Equals(desktopHandle) || hWnd.Equals(shellHandle))
                            {
                                RunningFullScreenApp = false;
                                break;
                            }
                            //判断是否全屏
                            if ((int)m.LParam == 1)
                                this.RunningFullScreenApp = true;
                            else
                                this.RunningFullScreenApp = false;
                            break;
                        }
                    default:
                        break;
                }
            }
            base.WndProc(ref m);
        }

使用方法：

RegisterAppBar(false);//注册该事件；

RegisterAppBar(true);//清除该事件；