optimizing parallel webservice calls

Question

In my project I have an async method AnAsynWebServiceCallHere for calling a web service. I want to call AnAsynWebServiceCallHere twice in parallel and at the end I want to return the combined result. Will at the end of this method

public async Task<List<DesiredResult>> GetMyDesiredData(MyParamDTO dto)
{
 List<DesiredResult> list = new List<DesiredResult>();
 await Task.WhenAll(
 Task.Run(()=> {var result1 = AnAsynWebServiceCallHere(dto.A);list.Add(result1);}), 
 Task.Run(()=> {var result2 = AnAsynWebServiceCallHere(dto.A);list.Add(result2);})
 );
 return list;
}

and body of the '' method is:

public async Task<DesiredResult> AnAsynWebServiceCallHere(string sqlQuery)
{
 string json;
 using(HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, "https://demoapi.MyHost.net/SQLRunner"))
 {
 request.Headers.Add("id", SECURITY_TOKEN); 
 request.Headers.Add("sqlStatement", sqlQuery);
 HttpResponseMessage response = await client.SendAsync(request);
 json = await response.Content.ReadAsStringAsync();
 }
 return JsonConvert.DeserializeObject<DesiredResult>(json);
}

Is the written method an elegant approach?

Update: Context provided with the called method body.

• t3chb0t: We cannot tell you whether this is an elegant approach or not becase this code isn't real and we don't review pseudo/hypothetical code.
• user1451111: This is a real code, just changed the method and object names from my real project. is the down-vote due to this reason?
• t3chb0t: Yes, the DV is for that reason and for not sharing enough context e.g. we don't know what's the signature of AnAsynWebServiceCallHere.
• t3chb0t: I find this still looks very much like pseudocode and thus voted against reopening but some people are of a different opinion so it might get reopened soon...

Answer 1

If AnAsynWebServiceCallHere is already async then there is no need for the additional Task.Run in the Task.WhenAll.

Task.WhenAll<TResult>(param Task<TResult>[]) will already return the results of the tasks in the collection as an array of results.

All that is left then is to convert the array to a List<>

public async Task<List<DesiredResult>> GetMyDesiredData(MyParamDTO dto) {
 var results = await Task.WhenAll(
 AnAsynWebServiceCallHere(dto.A), 
 AnAsynWebServiceCallHere(dto.A)
 );
 return results.ToList();
}

All the tasks will run in parallel and at the end will return the combined results.

Looking at the AnAsynWebServiceCallHere you could also wrap the response in a using statement as it is disposable also

public async Task<DesiredResult> AnAsynWebServiceCallHere(string sqlQuery) {
 var url = "https://demoapi.MyHost.net/SQLRunner";
 using(var request = new HttpRequestMessage(HttpMethod.Post, url)) {
 request.Headers.Add("id", SECURITY_TOKEN); 
 request.Headers.Add("sqlStatement", sqlQuery);
 using(HttpResponseMessage response = await client.SendAsync(request)) {
 var json = await response.Content.ReadAsStringAsync();
 return JsonConvert.DeserializeObject<DesiredResult>(json);
 }
 } 
}