【问题】
C#中，运行程序，异常：
Additional information: Exception has been thrown by the target of an invocation.
【解决过程】
1.后来，自己去看代码，好像看出问题了。
因为本身此处用的是BackgroundWorker，在completed函数中，用到了e.Result：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | private void bgwDownload_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e){ // The background process is complete. We need to inspect // our response to see if an error occurred, a cancel was // requested or if we completed successfully. // Check to see if an error occurred in the // background process. if (e.Error != null) { //MessageBox.Show(e.Error.Message); return; } // Check to see if the background process was cancelled. if (e.Cancelled) { //MessageBox.Show("Cancelled ..."); } else { bNotCompleted_download = false; // Everything completed normally. // process the response using e.Result //MessageBox.Show("Completed..."); gRealReadoutLen = (int)e.Result; }} |
但是，由于刚才不小心，在DoWork中，没有赋值e.Result：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | private void bgwDownload_DoWork(object sender, DoWorkEventArgs e) { // // The sender is the BackgroundWorker object we need it to // // report progress and check for cancellation. // BackgroundWorker gBgwDownload = sender as BackgroundWorker;。。。 try {。。。 do {。。。 curReadoutLen = binStream.Read(respBytesBuf, curBufPos, (int)expectReadoutLen); if (curReadoutLen > 0) {。。。 int currentPercent = (int)((currentLength * 100) / totalLength); if (currentPercent < 0) { currentPercent = 0; } if (currentPercent > 100) { currentPercent = 100; } gBgwDownload.ReportProgress(currentPercent); } } while (curReadoutLen > 0); } catch (Exception ex) { realReadoutLen = -1; } //return realReadoutLen; //e.Result = realReadoutLen; gBgwDownload.ReportProgress(100); } |
所以，此处，当调用BackgroundWorker的complete时候，即在bgwDownload_RunWorkerCompleted中，会执行到
1 | gRealReadoutLen = (int)e.Result; |
而此处e.Result，没有赋值，所以估计是null值，所以去执行：
1 | realReadoutLen = gRealReadoutLen; |
才出错的。
所以，去把e.Result加上：
1 2 3 4 5 6 7 8 9 | private void bgwDownload_DoWork(object sender, DoWorkEventArgs e){。。。 //return realReadoutLen; gBgwDownload.ReportProgress(100); e.Result = realReadoutLen;} |
【总结】
是自己不小心，在BackgroundWorker的DoWork中，把e.Result赋值漏掉了，所导致此问题。
加上后，就解决了。
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