IOException: 磁盘空间不足。

StackTrace:
   在 System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   在 System.IO.FileStream.WriteCore(Byte[] buffer, Int32 offset, Int32 count)
   在 System.IO.FileStream.Write(Byte[] array, Int32 offset, Int32 count)
   在 System.Windows.Media.Imaging.BitmapDownload.ReadCallback(IAsyncResult result)
   在 System.Net.LazyAsyncResult.Complete(IntPtr userToken)
   在 System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken)
   在 System.Net.Cache.ForwardingReadStream.ReadComplete(IAsyncResult transportResult)
   在 System.IO.FileStreamAsyncResult.AsyncFSCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOverlapped)
   在 System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)