为什么我的c#paint方法内存不足?

我对c#还很陌生,我试图通过编写一些简单的应用程序来学习,以熟悉语法和.NET库。我最近接的一个小项目是一个极钟 like the one found here .

我早期注意到的一个问题是,应用程序会不断“闪烁”,这确实会影响演示文稿的效果,因此我在网上阅读了有关如何实现双缓冲区的内容,它消除了这个问题,但可能与问题有关,也可能与问题无关。这是我的 onPaint 方法;计时器控件每33毫秒(~30 FPS)调用一次。应用程序的大部分其余部分只是用于拖动应用程序的处理程序(因为它是无框架的,并且有一个透明的背景)、双击退出等等。

    protected override void OnPaint(PaintEventArgs e) {
        DateTime now = DateTime.Now;

        float secondAngle = now.Second / 60F;
        secondAngle += (now.Millisecond / 1000F) * (1F / 60F);

        float minuteAngle = now.Minute / 60F;
        minuteAngle += secondAngle / 60F;

        float hourAngle = now.Hour / 24F;
        hourAngle += minuteAngle / 60F;

        float dayOfYearAngle = now.DayOfYear / (365F + (now.Year % 4 == 0 ? 1F : 0F));
        dayOfYearAngle += hourAngle / 24F;

        float dayOfWeekAngle = (float)(now.DayOfWeek + 1) / 7F;
        dayOfWeekAngle += hourAngle / 24F;

        float dayOfMonthAngle = (float)now.Day / (float)DateTime.DaysInMonth(now.Year, now.Month);
        dayOfMonthAngle += hourAngle / 24F;

        float monthAngle = now.Month / 12F;
        monthAngle += dayOfMonthAngle / (float)DateTime.DaysInMonth(now.Year, now.Month);

        float currentPos = brushWidth / 2F;

        float[] angles = {
            secondAngle, minuteAngle,
            hourAngle, dayOfYearAngle,
            dayOfWeekAngle, dayOfMonthAngle,
            monthAngle
        };

        SolidBrush DateInfo = new SolidBrush(Color.Black);
        SolidBrush background = new SolidBrush(Color.Gray);
        Pen lineColor = new Pen(Color.Blue, brushWidth);
        Font DateFont = new Font("Arial", 12);

        if (_backBuffer == null) {
            _backBuffer = new Bitmap(this.Width, this.Height);
        }

        Graphics g = Graphics.FromImage(_backBuffer);
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;

        try {                
            g.Clear(Color.White);
            if (_mouseIsOver) {
                g.FillEllipse(background, new Rectangle(0, 0, this.Width, this.Height));
            }
            foreach (float angle in angles) {
                g.DrawArc(
                    lineColor,
                    currentPos, currentPos,
                    this.Height - currentPos * 2, this.Width - currentPos * 2,
                    startAngle, angle * 360F
                );

                currentPos += brushWidth + spaceStep;
            }

            // Text - Seconds

            g.DrawString(String.Format("{0:D2} s", now.Second), DateFont, DateInfo, new PointF(115F, 0F));
            g.DrawString(String.Format("{0:D2} m", now.Minute), DateFont, DateInfo, new PointF(115F, 20F));
            g.DrawString(String.Format("{0:D2} h", now.Hour), DateFont, DateInfo, new PointF(115F, 40F));
            g.DrawString(String.Format("{0:D3}", now.DayOfYear), DateFont, DateInfo, new PointF(115F, 60F));
            g.DrawString(now.ToString("ddd"), DateFont, DateInfo, new PointF(115F, 80F));
            g.DrawString(String.Format("{0:D2} d", now.Day), DateFont, DateInfo, new PointF(115F, 100F));
            g.DrawString(now.ToString("MMM"), DateFont, DateInfo, new PointF(115F, 120F));
            g.DrawString(now.ToString("yyyy"), DateFont, DateInfo, new PointF(115F, 140F));

            e.Graphics.DrawImageUnscaled(_backBuffer, 0, 0);
        }
        finally {
            g.Dispose();
            DateInfo.Dispose();
            background.Dispose();
            DateFont.Dispose();
            lineColor.Dispose();
        }
        //base.OnPaint(e);
    }

    protected override void OnPaintBackground(PaintEventArgs e) {
        //base.OnPaintBackground(e);
    }

    protected override void OnResize(EventArgs e) {
        if (_backBuffer != null) {
            _backBuffer.Dispose();
            _backBuffer = null;
        }
        base.OnResize(e);
    }

我以为在方法结束时处理掉所有的东西会很安全,但似乎没有帮助。此外,运行时和OutOfMemoryException之间的间隔不是恒定的;一旦发生,只需几秒钟,但通常需要一两分钟。下面是一些类范围内的变量声明。

    private Bitmap _backBuffer;

    private float startAngle = -91F;
    private float brushWidth = 14;
    private float spaceStep = 6;

以及一个屏幕截图(编辑:屏幕截图链接到存在一些代码的视图):

_{(来源: ggot.org )}

编辑:Stacktrace!

System.OutOfMemoryException: Out of memory.
   at System.Drawing.Graphics.CheckErrorStatus(Int32 status)
   at System.Drawing.Graphics.DrawArc(Pen pen, Single x, Single y, Single width, Single height, Single startAngle, Single sweepAngle)
   at PolarClock.clockActual.OnPaint(PaintEventArgs e) in C:\Redacted\PolarClock\clockActual.cs:line 111
   at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)
   at System.Windows.Forms.Control.WmPaint(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

drawArc