Did you know there have different ways to consume a JSON Web API in .NET? In this post, it will show different methods to call an API.

1) Using WebClient

string GetApiByWebClient(string byQuery, string byHeader)
{
    using WebClient webClient = new WebClient();
    if (byHeader.Length > 0)
    {
        webClient.Headers.Add("name", byHeader);
    }
    webClient.Headers.Add("Accept", "application/json");
    webClient.Headers.Add("Content-Type", "application/json");
    return webClient.DownloadString(myApiUrl + (byQuery.Length == 0 ? "" : "?name=" + byQuery));
}

string PostApiByWebClient(string data)
{
    using WebClient webClient = new WebClient();
    webClient.Headers.Add("Accept", "application/json");
    webClient.Headers.Add("Content-Type", "application/json");
    return webClient.UploadString(myApiUrl, WebRequestMethods.Http.Post, data);
}

2) Using HttpWebRequest

string PostApiByHttpWebRequest(string data)
{
    HttpWebRequest webClient = (HttpWebRequest)WebRequest.Create(myApiUrl);
    webClient.Accept = "application/json";
    webClient.ContentType = "application/json";
    webClient.Method = WebRequestMethods.Http.Post;
    webClient.ContentLength = data.Length;
    using (var writer = new System.IO.StreamWriter(webClient.GetRequestStream()))
    {
        writer.Write(data);
    }
    var response = webClient.GetResponse() as HttpWebResponse;
    using (var streamReader = new StreamReader(response.GetResponseStream()))
    {
        return streamReader.ReadToEnd();
    }
}

3) Using HttpClient

async Task<string> PostApiByHttpClientAsync(string data)
{
    string result = "";

    using (var httpClient = new HttpClient())
    {
        httpClient.DefaultRequestHeaders.Add("Accept", "application/json");

        HttpContent httpContent = new StringContent(data);
        httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");

        using (HttpResponseMessage response = await httpClient.PostAsync(myApiUrl, httpContent))
        {
            if (response.Content != null && response.IsSuccessStatusCode)
            {
                result = await response.Content.ReadAsStringAsync();
            }
            else
            {
                if (response.Content != null)
                {
                    result = await response.Content.ReadAsStringAsync();
                    string message = "POST Response Fail : " + result;
                    throw new Exception(message);
                }
                else
                {
                    string message = "POST Response Fail : No response";
                    throw new Exception(message);
                }
            }
        }
    }

    return result;
}

Apparently, the third method is longer, but as you can see from the code, it is an asynchronous method, which means it is an efficient approach towards activities blocked or access is delayed e.g. Web API. Therefore, it is a recommended method if responsive is important for the application you want to develop.

Bonus:
4) Using Powershell
Lastly, how about after you deployed to an environment and it is not working? You not sure is it due to a firewall or network issue and you have no tools like POSTMAN….? Then, PowerShell can come to help.

PS D:\Temp\dotnetcore\ConsumeAPI> Invoke-WebRequest -Uri http://localhost:7071/api/HttpExample `
>>     -ContentType 'application/json' `
>>     -Method POST `
>>     -Body '{name: "POST API request from PowerShell"}'


StatusCode        : 200
StatusDescription : OK
Content           : Hello, POST API request from PowerShell.
RawContent        : HTTP/1.1 200 OK
                    Transfer-Encoding: chunked
                    Content-Type: text/plain; charset=utf-8
                    Date: Sat, 14 Aug 2021 09:16:38 GMT
                    Server: Kestrel

                    Hello, POST API request from PowerShell.
Forms             : {}
Headers           : {[Transfer-Encoding, chunked], [Content-Type, text/plain; charset=utf-8], [Date, Sat, 14 Aug 2021
                    09:16:38 GMT], [Server, Kestrel]}
Images            : {}
InputFields       : {}
Links             : {}
ParsedHtml        : mshtml.HTMLDocumentClass
RawContentLength  : 40