Question

这是我的代码，只是截取整个屏幕的截图。在它工作几次之后它就抛出了异常。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Imaging;

namespace Capture_ScreenShots
{
    public partial class Form1 : Form
    {
        string bfbc;
        string save_location;
        int save_image;
        int screenWidth;
        int screenHeight;

        public Form1()
        {
            InitializeComponent();
            save_location = @"c:\screenshots\sc1\";
            timer1.Enabled = true;
            timer1.Interval = 200;
            save_image = 0;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            save_image = save_image + 1;
            bfbc = save_location  + save_image.ToString("D3") + ".jpg";

            screenWidth = Screen.GetBounds(new Point(0, 0)).Width;
            screenHeight = Screen.GetBounds(new Point(0, 0)).Height;
            Bitmap bmpScreenShot = new Bitmap(screenWidth, screenHeight);
            Graphics gfx = Graphics.FromImage((Image)bmpScreenShot);
            gfx.CopyFromScreen(0, 0, 0, 0, new Size(screenWidth, screenHeight));
            bmpScreenShot.Save(bfbc, ImageFormat.Jpeg);
        }
    }
}

例外是在线：

gfx.CopyFromScreen(0, 0, 0, 0, new Size(screenWidth, screenHeight));

这是异常消息：

System.ComponentModel.Win32Exception was unhandled
  HResult=-2147467259
  Message=The operation completed successfully
  Source=System.Drawing
  ErrorCode=-2147467259
  NativeErrorCode=0
  StackTrace:
       at System.Drawing.Graphics.CopyFromScreen(Int32 sourceX, Int32 sourceY, Int32 destinationX, Int32 destinationY, Size blockRegionSize, CopyPixelOperation copyPixelOperation)
       at System.Drawing.Graphics.CopyFromScreen(Int32 sourceX, Int32 sourceY, Int32 destinationX, Int32 destinationY, Size blockRegionSize)
       at Capture_ScreenShots.Form1.timer1_Tick(Object sender, EventArgs e) in d:\C-Sharp\Capture_ScreenShots\Capture_ScreenShots\Capture_ScreenShots\Form1.cs:line 44
       at System.Windows.Forms.Timer.OnTick(EventArgs e)
       at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at Capture_ScreenShots.Program.Main() in d:\C-Sharp\Capture_ScreenShots\Capture_ScreenShots\Capture_ScreenShots\Program.cs:line 18
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

不确定异常发生的原因。它工作正常但只是很短的时间。

Answer 1

BitMap和Graphics都实现了IDisposible接口。

您不会在方法结束时处置您的对象。 using结构提供了一种简单的方法。

替换最后四行：

        Bitmap bmpScreenShot = new Bitmap(screenWidth, screenHeight);
        Graphics gfx = Graphics.FromImage((Image)bmpScreenShot);
        gfx.CopyFromScreen(0, 0, 0, 0, new Size(screenWidth, screenHeight));
        bmpScreenShot.Save(bfbc, ImageFormat.Jpeg);

使用：

        using (Bitmap bmpScreenShot = new Bitmap(screenWidth, screenHeight))
        using (Graphics gfx = Graphics.FromImage((Image)bmpScreenShot))
        {
            gfx.CopyFromScreen(0, 0, 0, 0, new Size(screenWidth, screenHeight));
            bmpScreenShot.Save(bfbc, ImageFormat.Jpeg);
        }

using构造确保这些类使用的系统资源是免费的，因此您不会遇到冲突。

Answer 2

消息来自NativeErrorCode == 0，这确实没有任何错误。

要查看实际失败，您必须查看HResult字段，即0x80004005。不幸的是，这是一个非常普遍的失败。

非零HResult和零NativeErrorCode的组合表示COM组件失败，它直接返回HRESULT而不使用SetLastError（）。

你唯一的其他线索是异常发生的地方。在图形处理的这种情况下，它肯定是一个失败的GDI +调用，因为GDI +是基于COM的，而GDI不是。

为什么我得到Win32Exception：操作成功完成？

2 个答案: