关于c＃：如何捕获此WPF位图加载异常？

How do I catch this WPF Bitmap loading exception?

我正在开发一个应用程序，它使用.NET3.5SP1和C_从Web上加载位图。

加载代码如下：

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try {
CurrentImage = pics[unChosenPics[index]];
bi = new BitmapImage(CurrentImage.URI);
// BitmapImage.UriSource must be in a BeginInit/EndInit block.
bi.DownloadCompleted += new EventHandler(bi_DownloadCompleted);
AssessmentImage.Source = bi;
}
catch {
System.Console.WriteLine("Something broke during the read!");
}

要加载到bi_下载完成的代码是：

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void bi_DownloadCompleted(object sender, EventArgs e) {
try {
double dpi = 96;
int width = bi.PixelWidth;
int height = bi.PixelHeight;

int stride = width * 4; // 4 bytes per pixel
byte[] pixelData = new byte[stride * height];
bi.CopyPixels(pixelData, stride, 0);

BitmapSource bmpSource = BitmapSource.Create(width, height, dpi, dpi, PixelFormats.Bgra32, null, pixelData, stride);

AssessmentImage.Source = bmpSource;
Loading.Visibility = Visibility.Hidden;
AssessmentImage.Visibility = Visibility.Visible;
}
catch {
System.Console.WriteLine("Exception when viewing bitmap.");
}
}

每一次，都会出现一幅让读者心碎的画面。我想这是意料之中的。然而，异常并没有被那些try/catch块捕获，而是被抛出到我可以处理的地方之外。我可以使用全局WPF异常来处理它，比如这个问题。但是，这会严重破坏我程序的控制流程，如果可能的话，我想避免这种情况。

我必须执行双源分配，因为在Microsoft位图加载器预期的位置，许多图像似乎缺少宽度/高度参数。因此，第一个分配似乎强制下载，第二个分配使dpi/图像尺寸正确发生。

我可以做什么来捕获和处理这个异常？

如果要复制，请尝试将此映像作为URI加载：

1	http://i.pbase.com/o2/26/519326/1/123513540.Yub8hciV.Longford12.jpg

例外情况本身是：

1 2	System.ArgumentException in PresentationCore Value does not fall within the expected range.

内部异常是：

1	An invalid character was found in text context.

堆栈跟踪：

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at MS.Internal.HRESULT.Check(Int32 hr)
at System.Windows.Media.Imaging.BitmapFrameDecode.get_ColorContexts()
at System.Windows.Media.Imaging.BitmapImage.FinalizeCreation()
at System.Windows.Media.Imaging.BitmapImage.OnDownloadCompleted(Object sender, EventArgs e)
at System.Windows.Media.UniqueEventHelper.InvokeEvents(Object sender, EventArgs args)
at System.Windows.Media.Imaging.LateBoundBitmapDecoder.DownloadCallback(Object arg)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
at System.Threading.ExecutionContext.runTryCode(Object userData)
at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Threading.DispatcherOperation.Invoke()
at System.Windows.Threading.Dispatcher.ProcessQueue()
at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Boolean isSingleParameter)
at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
at System.Windows.Threading.Dispatcher.TranslateAndDispatchMessage(MSG& msg)
at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
at System.Windows.Application.RunInternal(Window window)
at LensComparison.App.Main() in C:\Users\Mark64\Documents\Visual Studio 2008\Projects\LensComparison\LensComparison\obj
elease\App.g.cs:line 48
at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()