WinCE平台下C＃引用API（GDI）一个值得警惕的内存泄漏

由于C＃精简框架集绘图函数不支持圆角矩形，所以引用了相关的API。

 [DllImport("//windows//coredll.dll", EntryPoint = "RoundRect")]
        private static extern int CeRoundRect(IntPtr hdc, int X1, int Y1, int X2, int Y2, int X3, int Y3);

 这是有内存泄漏的源码：

 public static int RoundRect(Graphics e, Pen pen, SolidBrush brush, int X1, int Y1, int X2, int Y2, int X3, int Y3)
        {        
            IntPtr hpen;
            IntPtr hbrush;

            if(pen!=null)
            {
                hpen = CreatePen((DashStyle.Solid == pen.DashStyle) ? 0 : 1,
                (int)pen.Width, SetRGB(pen.Color.R, pen.Color.G, pen.Color.B));      //创建GDI画笔 
            }
            else
            {
                hpen = GetStockObject(8);      //空画笔
            }         

            if (brush!= null)
            {
                hbrush = CreateSolidBrush(SetRGB(brush.Color.R, brush.Color.G, brush.Color.B)); //brush.Color.ToArgb());
            }
            else
            {
                hbrush = GetStockObject(5);
            }

            //pen.Dispose();
            //brush.Dispose();

            IntPtr hdc = e.GetHdc();
            //---------------------   
             SelectObject(hdc, hbrush);
             SelectObject(hdc, hpen);

            int intRet=RoundRect(hdc, X1, Y1, X2,Y2, X3, Y3);

            DeleteObject(hbrush);
            DeleteObject(hpen);
            //---------------------
            e.ReleaseHdc(hdc);
            return intRet;
        }

这是没有问题的源码：

 public static int RoundRect(Graphics e, Pen pen, SolidBrush brush, int X1, int Y1, int X2, int Y2, int X3, int Y3)
        {        
            IntPtr hpen,old_pen;
            IntPtr hbrush, old_brush;

            if(pen!=null)
            {
                hpen = CreatePen((DashStyle.Solid == pen.DashStyle) ? 0 : 1,
                (int)pen.Width, SetRGB(pen.Color.R, pen.Color.G, pen.Color.B));      //创建GDI画笔 
            }
            else
            {
                hpen = GetStockObject(8);      //空画笔
            }         

            if (brush!= null)
            {
                hbrush = CreateSolidBrush(SetRGB(brush.Color.R, brush.Color.G, brush.Color.B)); //brush.Color.ToArgb());
            }
            else
            {
                hbrush = GetStockObject(5);
            }

            //pen.Dispose();
            //brush.Dispose();

            IntPtr hdc = e.GetHdc();
            //---------------------  
            old_brush=SelectObject(hdc, hbrush);
            old_pen=SelectObject(hdc, hpen);
           
            int intRet=RoundRect(hdc, X1, Y1, X2,Y2, X3, Y3);

            SelectObject(hdc, old_brush);
            SelectObject(hdc, old_pen);
            DeleteObject(hbrush);
            DeleteObject(hpen);
            //---------------------
            e.ReleaseHdc(hdc);
            return intRet;
        }

       看出代码的区别来了没有？泄漏的原因其实很简单，就是没有重新选入旧的画笔画刷。同样的程序（当然PC端的API库是GDI32）在上位机Window XP平台上没有什么问题（测试大约3天以上），而在WinCE平台确非常明显，大约1～3个小时（视圆角矩形绘图的多寡而定），该程序就会内存耗尽而死。