IOException
   在 System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   在 System.IO.FileStream.WriteCore(Byte[] buffer, Int32 offset, Int32 count)
   在 System.IO.FileStream.FlushInternalBuffer()
   在 System.IO.FileStream.Flush(Boolean flushToDisk)
   在 System.IO.FileStream.Flush()
   在 System.Windows.Media.Imaging.BitmapDownload.ReadCallback(IAsyncResult result)
   在 System.IO.FileStreamAsyncResult.CallUserCallbackWorker()
   在 System.IO.FileStreamAsyncResult.<>c.<CallUserCallback>b__39_0(Object state)
   在 System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state)
   在 System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   在 System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   在 System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   在 System.Threading.ThreadPoolWorkQueue.Dispatch()
   在 System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()