WPF最大化避免覆盖任务栏

WPF当窗体WindowStyle=”None”时，最大化会覆盖掉任务栏。如何解决这个问题呢？要用到Win32 API，通过让WPF窗体WM_GETMINMAXINFO消息挂接一个钩子来处理。

代码如下：

public static class WindowHelper
{
   public static void RepairWindowBehavior(Window wpfWindow)
   {
       if (wpfWindow == null )
           return ;

       wpfWindow.SourceInitialized += delegate
       {
           IntPtr handle = ( new WindowInteropHelper(wpfWindow)).Handle;
           HwndSource source = HwndSource.FromHwnd(handle);
           if (source != null )
           {
               source.AddHook(WindowProc);
           }
       };
   }

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

       return (IntPtr)0;
   }

   private static void WmGetMinMaxInfo(IntPtr hwnd, IntPtr lParam)
   {
       MINMAXINFO mmi = (MINMAXINFO)Marshal.PtrToStructure(lParam, typeof (MINMAXINFO));

       int MONITOR_DEFAULTTONEAREST = 0x00000002;
       IntPtr monitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST);

       if (monitor != 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 );
   }

   [DllImport( "user32" )]
   internal static extern bool GetMonitorInfo(IntPtr hMonitor, MONITORINFO lpmi);
   [DllImport( "User32" )]
   internal static extern IntPtr MonitorFromWindow(IntPtr handle, int flags);

   #region Nested type: MINMAXINFO
   [StructLayout(LayoutKind.Sequential)]
   internal struct MINMAXINFO
   {
       public POINT ptReserved;
       public POINT ptMaxSize;
       public POINT ptMaxPosition;
       public POINT ptMinTrackSize;
       public POINT ptMaxTrackSize;
   }
   #endregion

   #region Nested type: MONITORINFO
   [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
   internal class MONITORINFO
   {
       public int cbSize = Marshal.SizeOf( typeof (MONITORINFO));
       public RECT rcMonitor;
       public RECT rcWork;
       public int dwFlags;
   }
   #endregion

   #region Nested type: POINT
   [StructLayout(LayoutKind.Sequential)]
   internal struct POINT
   {
       public int x;
       public int y;
       public POINT( int x, int y)
       {
           this .x = x;
           this .y = y;
       }
   }
   #endregion

   #region Nested type: RECT
   [StructLayout(LayoutKind.Sequential, Pack = 0)]
   internal struct RECT
   {
       public int left;
       public int top;
       public int right;
       public int bottom;

       public static readonly RECT Empty;

       public int Width
       {
           get { return Math.Abs(right - left); }
       }
       public int Height
       {
           get { return bottom - top; }
       }

       public RECT( int left, int top, int right, int bottom)
       {
           this .left = left;
           this .top = top;
           this .right = right;
           this .bottom = bottom;
       }

       public RECT(RECT rcSrc)
       {
           left = rcSrc.left;
           top = rcSrc.top;
           right = rcSrc.right;
           bottom = rcSrc.bottom;
       }

       public bool IsEmpty
       {
           get
           {
               return left >= right || top >= bottom;
           }
       }

       public override string ToString()
       {
           if ( this == Empty)
           {
               return "RECT {Empty}" ;
           }
           return "RECT { left : " + left + " / top : " + top + " / right : " + right + " / bottom : " + bottom + " }" ;
       }

       public override bool Equals( object obj)
       {
           if (!(obj is Rect))
           {
               return false ;
           }
           return ( this == (RECT)obj);
       }

       public override int GetHashCode()
       {
           return left.GetHashCode() + top.GetHashCode() + right.GetHashCode() + bottom.GetHashCode();
       }

       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);
       }

       public static bool operator !=(RECT rect1, RECT rect2)
       {
           return !(rect1 == rect2);
       }
   }
   #endregion
}

通过调用WindowHelper.RepairWindowBehavior(Window)方法注册Win32消息事件，以后调用this.WindowState = WindowState.Maximized;就可以解决最大化避免覆盖任务栏的问题了。