How to consume rest api in C#

Question

I want to consume rest api having post method in my project (web)/Windows service(C#).

Url : https://sampleurl.com/api1/token

I need to pass username and password for generating token. I have written code like this.

string sURL = "https://sampleurl.com/api1/token/Actualusername/Actualpassword";
            WebRequest wrGETURL;
            wrGETURL = WebRequest.Create(sURL);

            wrGETURL.Method = "POST";
            wrGETURL.ContentType = @"application/json; charset=utf-8";
            wrGETURL.ContentLength = 0;
            HttpWebResponse webresponse = wrGETURL.GetResponse() as HttpWebResponse;

            Encoding enc = System.Text.Encoding.GetEncoding("utf-8");
            // read response stream from response object
            StreamReader loResponseStream = new StreamReader(webresponse.GetResponseStream(), enc);
            // read string from stream data
            string  strResult = loResponseStream.ReadToEnd();
            // close the stream object
            loResponseStream.Close();
            // close the response object
            webresponse.Close();

            Response.Write(strResult);

I am getting error: No connection could be made because the target machine actively refused it

Is it right way to consume rest api in C#?

Check this url http://stackoverflow.com/questions/18347055/calling-a-rest-api-with-username-and-password-how-to — S.K, May 17 '17 at 07:04
The rest server is not running, a firewall is blocking access to it or the url isn't right. I don't know about other browsers, but for Chrome there is an extension that allows you to test such requests: https://chrome.google.com/webstore/detail/advanced-rest-client/hgmloofddffdnphfgcellkdfbfbjeloo — C.Evenhuis, May 17 '17 at 07:17
So this API requires a POST method with no content and the username/password in the url? That seems like a really bad idea, maybe you are supposed to put the user credentials in the request body and send it? — robjam, May 17 '17 at 07:19
@robjam,thanks for ur help.Can u pls update the code?How to pass parameter in request body not in url?I — Jui Test, May 17 '17 at 07:24
Looks very non standard. Do you have any specifications for /api1/token end point? — Mardoxx, May 17 '17 at 07:25
@JuiTest How can we update your code to work with that api without knowing anything about that api? There should be a documentation how to consume the api. (just as an example the imgur api docs https://api.imgur.com/oauth2 ) — Sir Rufo, May 17 '17 at 07:53

score 3 · Accepted Answer · answered May 17 '17 at 07:54

This all very much depend on the API's documentation, but to write data to the request body, get the request stream and then write the string to the stream. again, this depends on what the API you are authenticating with and without knowing which one is guesswork on my part.

        string sURL = "https://sampleurl.com/api1/token";
        WebRequest wrGETURL;
        wrGETURL = WebRequest.Create(sURL);

        wrGETURL.Method = "POST";
        wrGETURL.ContentType = @"application/json; charset=utf-8";
        using (var stream = new StreamWriter(wrGETURL.GetRequestStream()))
        {
            var bodyContent = new
            {
                username = "Actualusername",
                password = "Actualpassword"
            }; // This will need to be changed to an actual class after finding what the specification sheet requires.

            var json = JsonConvert.SerializeObject(bodyContent);

            stream.Write(json);
        }
        HttpWebResponse webresponse = wrGETURL.GetResponse() as HttpWebResponse;

        Encoding enc = System.Text.Encoding.GetEncoding("utf-8");
        // read response stream from response object
        StreamReader loResponseStream = new StreamReader(webresponse.GetResponseStream(), enc);
        // read string from stream data
        string strResult = loResponseStream.ReadToEnd();
        // close the stream object
        loResponseStream.Close();
        // close the response object
        webresponse.Close();

        Response.Write(strResult);

I am using third party Rest api which made in PHP having post method.I don't know apart from this any other specification. — Jui Test, May 17 '17 at 07:56
Thanks Robjam for your help.Let me checked with ur code and revert u back. — Jui Test, May 17 '17 at 07:57
@JuiTest An API needs documentation. As a real world example this reads like "How to use my red car?" — Sir Rufo, May 17 '17 at 08:11
Thanks Robjam for code.I used ur code.I am getting Error :'An existing connection was forcibly closed by the remote host ' — Jui Test, May 17 '17 at 10:45
I can't really help anymore unless I can see the documentation. — robjam, May 17 '17 at 11:35

score 0 · Answer 2 · answered Jan 02 '20 at 15:14

Consume API with Basic Authentication in C#

 class Program
{
    static void Main(string[] args)
    {
        BaseClient clientbase = new BaseClient("https://website.com/api/v2/", "username", "password");
        BaseResponse response = new BaseResponse();
        BaseResponse response = clientbase.GetCallV2Async("Candidate").Result;
    }


    public async Task<BaseResponse> GetCallAsync(string endpoint)
    {
        try
        {
            HttpResponseMessage response = await client.GetAsync(endpoint + "/").ConfigureAwait(false);
            if (response.IsSuccessStatusCode)
            {
                baseresponse.ResponseMessage = await response.Content.ReadAsStringAsync();
                baseresponse.StatusCode = (int)response.StatusCode;
            }
            else
            {
                baseresponse.ResponseMessage = await response.Content.ReadAsStringAsync();
                baseresponse.StatusCode = (int)response.StatusCode;
            }
            return baseresponse;
        }
        catch (Exception ex)
        {
            baseresponse.StatusCode = 0;
            baseresponse.ResponseMessage = (ex.Message ?? ex.InnerException.ToString());
        }
        return baseresponse;
    }
}


public class BaseResponse
{
    public int StatusCode { get; set; }
    public string ResponseMessage { get; set; }
}

public class BaseClient
{
    readonly HttpClient client;
    readonly BaseResponse baseresponse;

    public BaseClient(string baseAddress, string username, string password)
    {
        HttpClientHandler handler = new HttpClientHandler()
        {
            Proxy = new WebProxy("http://127.0.0.1:8888"),
            UseProxy = false,
        };

        client = new HttpClient(handler);
        client.BaseAddress = new Uri(baseAddress);
        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        var byteArray = Encoding.ASCII.GetBytes(username + ":" + password);

        client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", Convert.ToBase64String(byteArray));

        baseresponse = new BaseResponse();

    }
}

How to consume rest api in C#

2 Answers2