Calling HttpClient asynchronously to get the HttpResponseMessage via ajax

Question

I am actually trying to fetch data through a URL using the HTTPClient class. I am calling via ajax call. However, when the response is fetched it gets back into running mode from debugging mode and nothing happens. No response is retrieved. Below is the code:

jQuery

$.ajax({
        type: "GET",
        contentType: "application/json; charset=utf-8",
        url: "../../Services/AService.asmx/GetCompanyInformation",
        data: { id: JSON.stringify(id) },
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        async:true,
        success: function (res) {
            var options = JSON.parse(res.d);                   

        },
        error: function (errormsg) {
            $(".dropdown_SubDomainLoading").hide();
            toastr.options.timeOut = 7000;
            toastr.options.closeButton = true;
            toastr.error('Something Went Wrong');
        }
    });

WebMethod Call

public static string CompanyDetails;

    [WebMethod]
    [ScriptMethod(UseHttpGet = true)]
    public string GetCompanyInformation(string id)
    {
        string authorizationKey = "Bearer 5cae498ef11f128363c1fbb2761bbab40ac0e2e5";
        string url = string.Empty;
        url = GetCompanyDetailsForApps(id);
        RunAsync(url).Wait();
        return CompanyDetails;
    }

 static async Task RunAsync(string Url)
    {
        string authorizationKey = "Bearer 5cae498ef11f128363c1fbb2761bbab40ac0e2e5";
        try
        {
            using (var client = new HttpClient())
            {
                client.BaseAddress = new Uri(Url);
                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Add("Authorization", authorizationKey);
                HttpResponseMessage response = await client.GetAsync(Url);

                if (response.IsSuccessStatusCode)
                {
                    string content = await response.Content.ReadAsStringAsync();
                    //UrlMetricsResponse mozResonse = JsonConvert.DeserializeObject<UrlMetricsResponse>(content);
                    dynamic dynObj = JsonConvert.DeserializeObject(content);
                    CompanyDetails = JsonConvert.SerializeObject(dynObj);
                }

            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("ERROR :" + ex.Message);
        }

    }

As soon as the client.GetAsync() function is called, it comes back to run mode and nothing is fetched. Am I doing something wrong. How can i retrieve the response via the url?

Most probably the call to client.GetAsync(Url) failed and it didn't go into the if block, so your CompanyDetails object is empty or null and that is returned to the client. If you set a break point exactly at the if statement, you should be able to see whats happening? — Thangadurai, Feb 22 '18 at 08:48
Possible duplicate of [An async/await example that causes a deadlock](https://stackoverflow.com/questions/15021304/an-async-await-example-that-causes-a-deadlock) — Leonid Vasilev, Feb 22 '18 at 08:49

score 1 · Accepted Answer · answered Feb 22 '18 at 13:28

Judging by [WebMethod], I'm guessing you are maintaining a very old ASP.NET application. The problem here is incompatible libraries. Old ASP.NET does not support async/await semantics, and HttpClient does not support synchronous HTTP operations.

Your best option is to upgrade the application to something more modern that supports async controllers, such as ASP.NET Web API or ASP.NET Core. This way you won't have to block threads on HTTP calls. But if this is not an option, you need swap out HttpClient for a library that actually supports synchronous/blocking HTTP. Have a look at WebRequest or RestSharp. If you continue to use HttpClient and there are .Result or .Wait() calls anywhere on the call stack, you're not only blocking but you are inviting deadlocks.

I can't stress this enough: HttpClient does not support synchronous HTTP, so if you can't switch to a more modern web framework, you must switch to an older HTTP library.

I tried the WebRequest part. But it is actually throwing error when the url is not correct rather that informing. While using HttpClient, it ask for **IsStatusCodeSucceeded**. However, with WebRequest, it plays with Statuscode. If found, it will pass else if will throw an exception. How can we overcome this situation in WebRequest? — Running Rabbit, Feb 23 '18 at 06:24
Not sure I understand. Maybe this will help https://learn.microsoft.com/en-us/dotnet/framework/network-programming/handling-errors — Todd Menier, Feb 23 '18 at 11:46

score 0 · Answer 2 · edited Feb 22 '18 at 09:23

0

Well, when I changed the client.GetAsync() to client.GetAsync().Result it worked.

edited Feb 22 '18 at 09:23

Rory McCrossan

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answered Feb 22 '18 at 09:07

Running Rabbit

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Please don't do that. It may have worked in your testing, but once you start adding concurrent users, you're eventually going to find yourself in deadlock hell. – Todd Menier Feb 22 '18 at 13:30
than what should I use.. as I am actually confused. – Running Rabbit Feb 22 '18 at 13:33
WebRequest or RestSharp. See my answer for details. – Todd Menier Feb 22 '18 at 13:35

Calling HttpClient asynchronously to get the HttpResponseMessage via ajax

2 Answers2