ASP.NET C# Posting to API and await Status in parallel

Question

I'm trying to come up with the correct architecture where I can send out a bunch of API posts requesting the GPS location of vehicles in a fleet. The objective is to blast out 10+ requests for status, then have each thread wait for a response then insert the result into a database table. The request and response is Json. I have the code working synchronously, one at a time, which can take 2 minutes per vehicle. my code is:

A client-side javascript timer triggers a submit btnGetData_Click

btnGetData_Click calls DoVehicleGetStatus():

public static async Task DoVehiclePollStatus()
int vehicleInfoId;            
string vehicleVIN;
string vehicleMileage;
string tokenId;
// Build DataSet with list of vehicle information needed to log in.

// Loop thru each Vehicle.
int iCount = ds.Tables[0].Rows.Count;
foreach (DataRow dr in ds.Tables[0].Rows)
{
 vehicleInfoId = Convert.ToInt32(dr["Id"]);                        
 vehicleVIN = dr["VehicleVIN"].ToString();
 vehicleMileage = dr["VehicleListMileage"].ToString();
 tokenId = dr["VehicleListToken"].ToString();

 // Serialize LoginInfo to Json            
 DataClass.GetStatusRequestBodyStruct getFromVehicle = new DataClass.GetStatusRequestBodyStruct();
 getFromVehicle.getFromVehicle = true;
 string requestJsonMessage = new JavaScriptSerializer().Serialize(getFromVehicle);

 DataClass.GetVehicleStatusStruct vs = new DataClass.GetVehicleStatusStruct();

 HttpClient httpClient = new HttpClient();

 httpClient.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type","application/json");

 StringContent httpContent = new StringContent(requestJsonMessage);

 // Set Header Parameters
 try
 {
   httpContent.Headers.TryAddWithoutValidation("tokenId", tokenId);
   httpContent.Headers.TryAddWithoutValidation("VIN", vehicleVIN);

   HttpResponseMessage response = await httpClient.PostAsync(new Uri(DataClass.API_URIGetVehicleStatus), httpContent);

   }
   catch (Exception ex)
   {
     errorMessage = ex.Message;
   }
   ....      
   ..save response (string) data in database...       

After hitting the await httpClient.PostAsync the program returns execution and I never get back a response from the request post. If this design is not correct, can you please suggest a better approach.

Answer 1

According to the error you are getting you should change public static async void DoVehiclePollStatus() to public static async Task DoVehiclePollStatus() . it Is not recommended to use async void.