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csharp/ExcelAddIn/factories/CredentialsDialogFactory.cs

@@ -29,22 +29,35 @@ void OnSetCredentialsButtonClicked() {
  var sharedTestCredentialsCookie = new SimpleAtomicReference<object>(new object());
 
  void TestCredentials(CredentialsBase creds) {
- // Set new version
+ // Make a unique sentinel object to indicate that this thread should be
+ // the one privileged to provide the system with the answer to the "Test
+ // Credentials" question. If the user doesn't press the button again,
+ // we will go ahead and provide our answer to the system. However, if the
+ // user presses the button again, triggering a new thread, then that
+ // new thread will usurp our privilege and it will be the one to provide
+ // the answer.
  var localLatestTcc = new object();
  sharedTestCredentialsCookie.Value = localLatestTcc;
 
  var state = "OK";
  try {
+ // This operation might take some time.
  var temp = SessionBaseFactory.Create(creds, sm.WorkerThread);
  temp.Dispose();
  } catch (Exception ex) {
  state = ex.Message;
  }
 
- // true if the button was wasn't pressed again in the meantime
- if (ReferenceEquals(localLatestTcc, sharedTestCredentialsCookie.Value)) {
- credentialsDialog!.SetTestResultsBox(state);
+ // If sharedTestCredentialsCookie is still the same, then our privilege
+ // has not been usurped and we can provide our answer to the system.
+ // On the other hand, if it changes, then we will just throw away our work.
+ if (!ReferenceEquals(localLatestTcc, sharedTestCredentialsCookie.Value)) {
+ // Our results are moot. Dispose of them.
+ return;
  }
+
+ // Our results are valid. Keep them and tell everyone about it.
+ credentialsDialog!.SetTestResultsBox(state);
  }
 
  void OnTestCredentialsButtonClicked() {

csharp/ExcelAddIn/providers/SessionProvider.cs

@@ -91,18 +91,28 @@ public void SetCredentials(CredentialsBase credentials) {
  }
 
  void CreateSessionBaseInSeparateThread(CredentialsBase credentials) {
+ // Make a unique sentinel object to indicate that this thread should be
+ // the one privileged to provide the system with the Session corresponding
+ // to the credentials. If SetCredentials isn't called in the meantime,
+ // we will go ahead and provide our answer to the system. However, if
+ // SetCredentials is called again, triggering a new thread, then that
+ // new thread will usurp our privilege and it will be the one to provide
+ // the answer.
  var localLatestCookie = new object();
  _sharedSetCredentialsCookie.Value = localLatestCookie;
 
  StatusOr<SessionBase> result;
  try {
+ // This operation might take some time.
  var sb = SessionBaseFactory.Create(credentials, workerThread);
  result = StatusOr<SessionBase>.OfValue(sb);
  } catch (Exception ex) {
  result = StatusOr<SessionBase>.OfStatus(ex.Message);
  }
 
- // By the time we get here, some time has passed. Have our results become moot?
+ // If sharedTestCredentialsCookie is still the same, then our privilege
+ // has not been usurped and we can provide our answer to the system.
+ // On the other hand, if it has changed, then we will just throw away our work.
  if (!ReferenceEquals(localLatestCookie, _sharedSetCredentialsCookie.Value)) {
  // Our results are moot. Dispose of them.
  if (result.GetValueOrStatus(out var sb, out _)) {