trouble shooting System.AggregateException - c#-4.0

Question

I need another pair of eyes to take a look at this. It's driving me nuts.
I am intermittently getting a 'System.AggregateException' when running a console app that connects to a web api.
I am doing this in a local testing environment through visual studio(IIS Express).
As stated, I have two different apps running locally on IIS Express(2 different ports). One is a console app and the other is a web api. The console app connects to the web api.
It's about 50/50 if it works or not. 50% of the time it works fine and spits out the expected results. But the other 50% of the time, it fails with the errors below. When it does fail, it's always immediate, like 2 or 3 seconds after starting the console app.
After some Googling and fiddling around with various settings, I know it's not either of these:
not a timeout issue
not a firewall issue
I've tried setting breakpoints at various points, but it never really reveals anything significant.
The exception I get when it fails is:
An exception of type 'System.AggregateException' occurred in mscorlib.dll but was not handled in user code
Here is the inner exception:
No connection could be made because the target machine actively refused it http://localhost:45321
The stack trace indicates:
at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context)
at System.Net.Http.HttpClientHandler.GetRequestStreamCallback(IAsyncResult ar)
at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task1.GetResultCore(Boolean waitCompletionNotification)
at System.Threading.Tasks.Task1.get_Result()
at BeatGenerator.BeatGeneratorMain.<>c.b__2_0(Task1 postTask) in C:\Users\xxx\Documents\VS2012\DrumBeats\BeatGenerator\BeatGeneratorMain.cs:line 72
at System.Threading.Tasks.ContinuationResultTaskFromResultTask2.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
Here is the error line:
var response = await http.PostAsJsonAsync("http://localhost:45321/api/drumcorp/beats/generate", drumbeat)
.ContinueWith((postTask) => postTask.Result.EnsureSuccessStatusCode());
This is the console app that connects to API controller:
public class DrumBeats
{
public int StartBeat { get; set; }
public int EndBeat { get; set; }
public int ChordId { get; set; }
}
public class BeatGeneratorMain
{
static void Main(string[] args)
{
Generate().Wait();
}
private static async Task Generate()
{
var drumbeat = new DrumBeats();
drumbeat.ChordId = 122;
drumbeat.StartBeat = 2;
drumbeat.EndBeat = 4;
var creds = new NetworkCredential("testUser", "xxxx", "xxx"); //username, pw, domain
var handler = new HttpClientHandler { Credentials = creds };
using (var http = new HttpClient(handler))
{
http.Timeout = TimeSpan.FromMinutes(10);
var response = await http.PostAsJsonAsync("http://localhost:45321/api/drumcorp/beats/generate", drumbeat)
.ContinueWith((postTask) => postTask.Result.EnsureSuccessStatusCode());
var result = await response.Content.ReadAsStringAsync();
Console.WriteLine(result);
}
}
}
This is the relevant section of the web api controller app:
public class DrumBeats //same as in console app
{
public int StartBeat { get; set; }
public int EndBeat { get; set; }
public int ChordId { get; set; }
}
[HttpPost("api/drumcorp/beats/generate")]
public string PostMethodBeats([FromBody] DrumBeats drumbeat)
{
string beatsChart = DrumBeatMaster.ReturnBeatsChart(DrumBeats.ChordId, DrumBeats.StartBeat, DrumBeats.EndBeat);
var mesg = "<b>Beats Created</b><br /><br /> ";
return mesg + beatsChart;
}
DrumBeatMaster.ReturnBeatsChart is just a simple helper method that processes the beats and spits out a string.

Answer 1

To understand what is the exception you will have to catch the aggregate exception and throw them flattened like
try
{
// Your code
}
catch (AggregateException agg)
{
throw agg.Flatten();
}