WindowState=WindowState.Maximized不遮住任务栏(WPF)

前提：WindowStyle="None" ResizeMode="NoResize"

Step1:在窗体构造函数中加SourceInitialized事件

   public MainWindow()
        {
            InitializeComponent();
            SourceInitialized += MainWindow_SourceInitialized;
        }

Step2:事件处理

  private void MainWindow_SourceInitialized(object sender, EventArgs e)
        {
            IntPtr handle = (new WinInterop.WindowInteropHelper(this)).Handle;
            WinInterop.HwndSource.FromHwnd(handle).AddHook(new WinInterop.HwndSourceHook(WindowProcHelper.WindowProc));
        }

Step3:具体处理类WindowProcHelper

public class WindowProcHelper
    {
        public static System.IntPtr WindowProc(
           System.IntPtr hwnd,
           int msg,
           System.IntPtr wParam,
           System.IntPtr lParam,
           ref bool handled)
        {
            switch (msg)
            {
                case 0x0024:
                WmGetMinMaxInfo(hwnd, lParam);
                handled = true;
                break;
            }

            return (System.IntPtr)0;
        }

        private static void WmGetMinMaxInfo(System.IntPtr hwnd, System.IntPtr lParam)
        {

            MINMAXINFO mmi = (MINMAXINFO)Marshal.PtrToStructure(lParam, typeof(MINMAXINFO));

            // Adjust the maximized size and position to fit the work area of the correct monitor
            #region old
            //int MONITOR_DEFAULTTONEAREST = 0x00000002;
            //System.IntPtr monitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST);

            //if (monitor != System.IntPtr.Zero)
            //{

            //    MONITORINFO monitorInfo = new MONITORINFO();
            //    GetMonitorInfo(monitor, monitorInfo);
            //    RECT rcWorkArea = monitorInfo.rcWork;
            //    RECT rcMonitorArea = monitorInfo.rcMonitor;
            //    mmi.ptMaxPosition.x = Math.Abs(rcWorkArea.left - rcMonitorArea.left);
            //    mmi.ptMaxPosition.y = Math.Abs(rcWorkArea.top - rcMonitorArea.top);
            //    mmi.ptMaxSize.x = Math.Abs(rcWorkArea.right - rcWorkArea.left);
            //    mmi.ptMaxSize.y = Math.Abs(rcWorkArea.bottom - rcWorkArea.top);
            //}

            //Marshal.StructureToPtr(mmi, lParam, true);
            #endregion
            int widthFullScreen = 0;
            int heightFullScreen = 0;
            Screen screen = null;
            if (SystemInformation.MonitorCount >= 1)
                screen = Screen.FromHandle(hwnd);
            if (screen != null)
            {
                widthFullScreen = screen.WorkingArea.Width;
                heightFullScreen = screen.WorkingArea.Height;
            }
            else
            {
                widthFullScreen = Screen.PrimaryScreen.Bounds.Width;
                heightFullScreen = Screen.PrimaryScreen.Bounds.Height;
            }
            mmi.ptMaxTrackSize.x = widthFullScreen + (int)(2*SystemParameters.FixedFrameVerticalBorderWidth);
            mmi.ptMaxTrackSize.y = heightFullScreen + (int)(2 * SystemParameters.FixedFrameHorizontalBorderHeight);

            Marshal.StructureToPtr(mmi,lParam,false);
        }


        /// <summary>
        /// POINT aka POINTAPI
        /// </summary>
        [StructLayout(LayoutKind.Sequential)]
        public struct POINT
        {
            /// <summary>
            /// x coordinate of point.
            /// </summary>
            public int x;
            /// <summary>
            /// y coordinate of point.
            /// </summary>
            public int y;

            /// <summary>
            /// Construct a point of coordinates (x,y).
            /// </summary>
            public POINT(int x, int y)
            {
                this.x = x;
                this.y = y;
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct MINMAXINFO
        {
            public POINT ptReserved;
            public POINT ptMaxSize;
            public POINT ptMaxPosition;
            public POINT ptMinTrackSize;
            public POINT ptMaxTrackSize;
        };
        /// <summary>
        /// </summary>
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        public class MONITORINFO
        {
            /// <summary>
            /// </summary>            
            public int cbSize = Marshal.SizeOf(typeof(MONITORINFO));

            /// <summary>
            /// </summary>            
            public RECT rcMonitor = new RECT();

            /// <summary>
            /// </summary>            
            public RECT rcWork = new RECT();

            /// <summary>
            /// </summary>            
            public int dwFlags = 0;
        }


        /// <summary> Win32 </summary>
        [StructLayout(LayoutKind.Sequential, Pack = 0)]
        public struct RECT
        {
            /// <summary> Win32 </summary>
            public int left;
            /// <summary> Win32 </summary>
            public int top;
            /// <summary> Win32 </summary>
            public int right;
            /// <summary> Win32 </summary>
            public int bottom;

            /// <summary> Win32 </summary>
            public static readonly RECT Empty = new RECT();

            /// <summary> Win32 </summary>
            public int Width
            {
                get { return Math.Abs(right - left); }  // Abs needed for BIDI OS
            }
            /// <summary> Win32 </summary>
            public int Height
            {
                get { return bottom - top; }
            }

            /// <summary> Win32 </summary>
            public RECT(int left, int top, int right, int bottom)
            {
                this.left = left;
                this.top = top;
                this.right = right;
                this.bottom = bottom;
            }


            /// <summary> Win32 </summary>
            public RECT(RECT rcSrc)
            {
                this.left = rcSrc.left;
                this.top = rcSrc.top;
                this.right = rcSrc.right;
                this.bottom = rcSrc.bottom;
            }

            /// <summary> Win32 </summary>
            public bool IsEmpty
            {
                get
                {
                    // BUGBUG : On Bidi OS (hebrew arabic) left > right
                    return left >= right || top >= bottom;
                }
            }
            /// <summary> Return a user friendly representation of this struct </summary>
            public override string ToString()
            {
                if (this == RECT.Empty) { return "RECT {Empty}"; }
                return "RECT { left : " + left + " / top : " + top + " / right : " + right + " / bottom : " + bottom + " }";
            }

            /// <summary> Determine if 2 RECT are equal (deep compare) </summary>
            public override bool Equals(object obj)
            {
                if (!(obj is Rect)) { return false; }
                return (this == (RECT)obj);
            }

            /// <summary>Return the HashCode for this struct (not garanteed to be unique)</summary>
            public override int GetHashCode()
            {
                return left.GetHashCode() + top.GetHashCode() + right.GetHashCode() + bottom.GetHashCode();
            }


            /// <summary> Determine if 2 RECT are equal (deep compare)</summary>
            public static bool operator ==(RECT rect1, RECT rect2)
            {
                return (rect1.left == rect2.left && rect1.top == rect2.top && rect1.right == rect2.right && rect1.bottom == rect2.bottom);
            }

            /// <summary> Determine if 2 RECT are different(deep compare)</summary>
            public static bool operator !=(RECT rect1, RECT rect2)
            {
                return !(rect1 == rect2);
            }


        }

        [DllImport("user32")]
        internal static extern bool GetMonitorInfo(IntPtr hMonitor, MONITORINFO lpmi);

        /// <summary>
        /// 
        /// </summary>
        [DllImport("User32")]
        internal static extern IntPtr MonitorFromWindow(IntPtr handle, int flags);
    }

　　

参考：

https://docs.microsoft.com/en-us/archive/blogs/llobo/maximizing-window-with-windowstylenone-considering-taskbar

https://social.msdn.microsoft.com/Forums/en-US/37e66890-9dbb-4de9-a228-c35633c2974c/windowstatemaximized-hides-the-taskbar?forum=wpf