首页 > 解决方案 > 为什么我收到异常 System.Reflection.TargetInvocationException: 'Exception has been throwed by the target of an invocation.'?

问题描述

ExternalException: A generic error occurred in GDI+.


System.Reflection.TargetInvocationException
HResult=0x80131604
Message=Exception has been thrown by the target of an invocation.
Source=mscorlib
StackTrace:
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
at System.Delegate.DynamicInvokeImpl(Object[] args)
at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj)
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.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
at System.Windows.Forms.Control.InvokeMarshaledCallbacks()
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.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 Extract.Program.Main() in D:\Csharp Projects\Extract\Program.cs:line 19

This exception was originally thrown at this call stack:
System.Drawing.Image.Save(string, System.Drawing.Imaging.ImageCodecInfo, System.Drawing.Imaging.EncoderParameters)
System.Drawing.Image.Save(string, System.Drawing.Imaging.ImageFormat)
Extract.Form1.DownloadAsync() in Form1.cs
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(System.Threading.Tasks.Task)
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(System.Threading.Tasks.Task)
System.Runtime.CompilerServices.TaskAwaiter.GetResult()
Extract.Form1.DownloadImages() in Form1.cs
System.Runtime.CompilerServices.AsyncMethodBuilderCore.ThrowAsync.AnonymousMethod__6_0(object)

Inner Exception 1:
ExternalException: A generic error occurred in GDI+.

列表图像和日期都包含 23 项。异常不是超出索引,而是在最后一项 23 上抛出异常。它在所有图像上绘制文本,但在第 23 项的循环结束时抛出异常。

if (images.Length > 0)
{
for (int i = 0; i < images.Length; i++)
{
drawOnImage.DrawText(dates[i].ToString("ddd, dd MMM yyy HH':'mm"), images[i]);
}
}

也许是因为两个列表包含相同数量的项目 23 ?那我该怎么解决呢?

这是 DownloadAsync 方法的完整代码,在底部我使用 memorystream 和内部带有 drawtext 的循环,异常仅在循环完成时发生在最后一项上。

private async Task DownloadAsync()
         {
             using (var client = new WebClient())
             {
                 client.DownloadFileCompleted += (s, e) =>
                 {
                     if (e.Error == null)
                     {
                         urlsCounter--;
    
                         var t = urls;
    
                         if (urlsCounter == 0)
                         {
                             CheckIfImagesExist();
    
                             btnRadarPath.Enabled = true;
                             btnSatellitePath.Enabled = true;
    
                             radCounter = 0;
                             satCounter = 0;
    
                             lblStatus.Text = "Completed.";
    
                             dates = rad.dates;
                             var images = System.IO.Directory.GetFiles(radarFolderImagesDownload,
                                   "*.gif", SearchOption.AllDirectories).OrderBy(x => x).ToArray();
    
                             Array.Sort(images, new MyComparer(false));
    
                             if (images.Length > 0)
                             {
                                 for (int i = 0; i < images.Length; i++)
                                 {
                                     drawOnImage.DrawText(dates[i].ToString("ddd, dd MMM yyy HH':'mm"), images[i]);
                                 }
                             }
    
                             GetImagesFiles();
                         }
                     }
                     else
                     {
                         string error = e.Error.ToString();
                     }
                 };
    
                 client.DownloadDataCompleted += (s, e) =>
                 {
                     if (e.Error == null)
                     {
                         urlsCounter--;
    
                         var t = urls;
    
                         if (urlsCounter == 0)
                         {
                             CheckIfImagesExist();
    
                             btnRadarPath.Enabled = true;
                             btnSatellitePath.Enabled = true;
    
                             radCounter = 0;
                             satCounter = 0;
    
                             lblStatus.Text = "Completed.";
    
                             dates = rad.dates;
                             var images = System.IO.Directory.GetFiles(radarFolderImagesDownload,
                                   "*.gif", SearchOption.AllDirectories).OrderBy(x => x).ToArray();
    
                             Array.Sort(images, new MyComparer(false));
    
                             if (images.Length > 0)
                             {
                                 for (int i = 0; i < images.Length; i++)
                                 {
                                     drawOnImage.DrawText(dates[i].ToString("ddd, dd MMM yyy HH':'mm"), images[i]);
                                 }
                             }
    
                             GetImagesFiles();
                         }
                     }
                 };
    
                 client.DownloadProgressChanged += (s, e) => tracker.SetProgress(e.BytesReceived, e.TotalBytesToReceive);
                 client.DownloadProgressChanged += (s, e) => lblAmount.Text = tracker.SizeSuffix(e.BytesReceived) + "/" + tracker.SizeSuffix(e.TotalBytesToReceive);
                 client.DownloadProgressChanged += (s, e) => lblSpeed.Text = tracker.GetBytesPerSecondString();
                 client.DownloadProgressChanged += (s, e) => myLong = Convert.ToInt64(client.ResponseHeaders["Content-Length"]);
                 client.DownloadProgressChanged += (s, e) =>
                 {
                     progressBar1.Value = e.ProgressPercentage;
                     label1.Text = e.ProgressPercentage + "%";
                 };
    
                 for (int i = 0; i < urls.Count; i++)
                 {
                     tracker.NewFile();
    
                     if (urls[i].Contains("Radar"))
                     {
                         await client.DownloadFileTaskAsync(new Uri(urls[i]), radarFolderImagesDownload + "\\image" + radCounter + ".gif");
    
                         radCounter++;
                     }
                     else
                     {
                         lblStatus.Text = "Downloading satellite";
    
                         using (MemoryStream ms = new MemoryStream(await client.DownloadDataTaskAsync(new Uri(urls[i]))))
                         {
                             Image img = Image.FromStream(ms, true);
                             img.Save(satelliteFolderImagesDownload + "\\image" + satCounter + ".gif", System.Drawing.Imaging.ImageFormat.Gif);
                         }
    
                         satCounter++;
                     }
                 }
             }
         }

标签: c#winforms

解决方案


猜测这是发生在与主线程不同的线程中。如果是这样,您需要调用 UI 调用 (DrawText)。为此,您可以将 Invoke 与委托一起使用。为了更彻底,您可以检查InvokeRequired您是否确实需要调用该调用(即您在不同的线程上)。

Invoke(new Action(() =>
{
    drawOnImage.DrawText(dates[i].ToString("ddd, dd MMM yyy HH':'mm"), images[i]);
}));

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