Using async/await and returning Task<HttpResponseMessage> From ASP.NET Web API Methods

Question

I have a Portable Class Library (PCL) method like this:

public async Task<string> GetLineStatuses()
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
    using (HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync())
    {
        return response.GetResponseStream().ReadAllText();
    }
}

My ASP.NET Web Api method looks like this:

public async Task<HttpResponseMessage> Get()
{
    HttpResponseMessage response = new HttpResponseMessage();
    string statuses = await service.GetStatuses();
    response.Content = new StringContent(statuses);
    return response;
}

What are the implications of returning a Task in Web API. Is this allowed? The only reason I want to use await is so I can use a Portable Class Library (PCL). What is the best practice? Should I have a syncronous version of my method and an asyncronous version? What are the performance and code readability and maintainability implications?

Also would I have the same effect if I returned Task<string> rather than Task<HttpResponseMessage>?

I belive ASP.NET in .Net 4.5 does support async methods, so your code should work fin. Why are you asking if this is allowed? Didn't you try it out? — svick
– svick, Commented Dec 28, 2012 at 13:05
I also want to know what the performance and code readability and maintainability implications? — Muhammad Rehan Saeed
– Muhammad Rehan Saeed, Commented Feb 25, 2015 at 9:13

Pete · Accepted Answer · 2012-12-28 14:19:22Z

5

Async and await are perfectly acceptable in ASP.NET. Here's a Scott Handselman video demoing it: http://www.asp.net/vnext/overview/aspnet/async-and-await

"Also would I have the same effect if I returned Task<string> rather than Task<HttpResponseMessage>?"

Not really sure what you mean by this. The Task is like a container for the object, so a Task<string> would contain your string result and a Task<HttpResponseMessage> would contain your HttpResponseMessage result... Is that what you mean? I think either method is perfectly acceptable. If you just need the string, then go with that. No point in returning more than you need.

answered Dec 28, 2012 at 14:19

Pete

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3 Comments

Muhammad Rehan Saeed Over a year ago

In Web API, you can return any object you want to be serialized as the content or return a HttpResponseMessage. Thats what I meant.

Pete Over a year ago

I'm still not following you. Keep in mind, it's not returning a string, but a Task<string>. The string, in Task<string>.Result can be rendered as content, but a Task<string> itself cannot.

Youssef Moussaoui Over a year ago

Returning a string and returning an HttpResponseMessage with a StringContent and two different things. If you return a string, WebAPi will use content negotiation to find a formatter that can serialize that string. If you return a StringContent, that string goes out directly in the response. But returning a Task<string> that completes eventually with a string should be equivalent to returning that string directly as far as WebAPI is concerned.

Power Mouse · Accepted Answer · 2019-04-24 18:51:12Z

as alternative:

public static async Task<string> CallGET(string requestUri, string id = "")
{
    string responseData;
    using (var client = new HttpClient(new HttpClientHandler() { UseDefaultCredentials = true }))
    {
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

        Uri.TryCreate(new Uri(baseURI), $"{requestUri}{(string.IsNullOrEmpty(id) ? string.Empty : $"/{id}")}", out Uri fullRequestUri);
        using (var response = await client.GetAsync(fullRequestUri))
        {
            responseData = await response.Content.ReadAsStringAsync();
        }
        return responseData;
    }
}

and call would be:

var getListUsersResult = Utils.CallGET($"/v1/users").Result;
var resultset= JsonConvert.DeserializeObject(getListUsersResult, typeof(List<UsersDTO>)) as List<UsersDTO>;
UserDTO r = users.Where(d => d.Name.ToLower().Contains("test")).FirstOrDefault();

and another call for one item:

var getUser = Utils.CallGET($"/v1/users", $"{USER_ID}").Result;
var getUserResponse = JsonConvert.DeserializeObject(getUser, typeof(UserDTO)) as UserDTO;

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