C# Http Post - Return Response to Main Program

Question

Using C# - How may I have the function return the response back to the main program?

I tried adding Task string to the function along with adding string response = cls.PostData(accesstoken, thejsondata).Wait(); to the call from Main. I am guessing I am not understanding the asynchronous aspect.

// From the main program
CallingClass cls = new CallingClass();
cls.PostData(accesstoken, thejsondata).Wait();
// want the "body" of data returned here?

public class CallingClass
{

  private static readonly HttpClient client = new HttpClient();


        public async Task PostData(string accesstoken, string thejsondata)
        {
                      
            var request = new HttpRequestMessage
            {
                Method = HttpMethod.Post,
                RequestUri = new Uri("https://whateverurl.com/"),              
                
                Headers =
                {
                    { "Authorization", accesstoken }
                },
                */
                Content = new StringContent(thejsondata))

                {
                    Headers =
                    {
                        ContentType = new MediaTypeHeaderValue("application/json")
                    }
                }
            };
            using (var response = await client.SendAsync(request))
            {
                response.EnsureSuccessStatusCode();
                var body = await response.Content.ReadAsStringAsync();
                Int32 responseStatusCode = (Int32)response.StatusCode;
                if (responseStatusCode.ToString() == "200" || responseStatusCode.ToString() == "201")
                {
                    hlp.AddToOutputFolder("StatusCode -  " + responseStatusCode.ToString());
                    hlp.AddToOutputFolder("Response -  " + body);
                }
                else
                {
                    hlp.AddToOutputFolder("ERROR RESPONSE STRING= " + responseStatusCode.ToString());
                }

                //return body;

            }
           
        }

}

Answer 1

You are returning a Task which is going to be giving you back void. You won't be able to store that response to a variable for later use in Main(). What you need to do is change the return type, await the method, and assign to a var for use

public class App
{
    public static async Task Main(string[] args)
    {
        CallingClass cls = new CallingClass();
        string postResponse = await cls.PostData(accesstoken, thejsondata); //don't need .Wait(), use await

        //now do stuff with postResponse...
    }
}

public class CallingClass
{
    private static readonly HttpClient client = new HttpClient();


    public async Task<string> PostData(string accesstoken, string thejsondata)
    {
        HttpRequestMessage request = new()
        {
            Method = HttpMethod.Post,
            RequestUri = new Uri("https://whateverurl.com/"),              
            Headers =
            {
                { "Authorization", accesstoken }
            },
            Content = new StringContent(thejsondata)
            {
                Headers =
                {
                    ContentType = new MediaTypeHeaderValue("application/json")
                }
            }
        };

        using (response = await client.SendAsync(request))
        {
            response.EnsureSuccessStatusCode();
            string body = await response.Content.ReadAsStringAsync();
            int responseStatusCode = (int) response.StatusCode;
            if (response.StatusCode == HttpStatusCode.OK || response.StatusCode == HttpStatusCode.Created)
            {
                hlp.AddToOutputFolder("StatusCode -  " + responseStatusCode.ToString());
                hlp.AddToOutputFolder("Response -  " + body);
            }
            else
            {
                hlp.AddToOutputFolder("ERROR RESPONSE STRING= " + responseStatusCode.ToString());
            }

            return body;
        }
    }
}

You can never assign a void method's "return" to a variable, not even with the discard operator _ = MyVoidMethod(); so its the same sort of thing here. A void method returns nothing. await is going to unwrap what you actually need from Task<T> and that T must match the typing of the variable you want to assign the return to

You should also give this SO question a read as the await operator and the .Wait() method are different things altogether and cannot be used interchangeably