How to make an HTTP POST web request

There are several ways to perform HTTP GET and POST requests:

Method A: HttpClient (Preferred)

Available in: .NET Framework 4.5+, .NET Standard 1.1+, and .NET Core 1.0+.

It is currently the preferred approach, and is asynchronous and high performance. Use the built-in version in most cases, but for very old platforms there is a NuGet package.

using System.Net.Http;

Setup

It is recommended to instantiate one HttpClient for your application's lifetime and share it unless you have a specific reason not to.

private static readonly HttpClient client = new HttpClient();

See HttpClientFactory for a dependency injection solution.

  • POST

      var values = new Dictionary<string, string>
  {
      { "thing1", "hello" },
      { "thing2", "world" }
  };

  var content = new FormUrlEncodedContent(values);

  var response = await client.PostAsync("http://www.example.com/recepticle.aspx", content);

  var responseString = await response.Content.ReadAsStringAsync();

  • GET

      var responseString = await client.GetStringAsync("http://www.example.com/recepticle.aspx");

Method B: Third-Party Libraries

RestSharp

  • POST

       var client = new RestClient("http://example.com");
   // client.Authenticator = new HttpBasicAuthenticator(username, password);
   var request = new RestRequest("resource/{id}");
   request.AddParameter("thing1", "Hello");
   request.AddParameter("thing2", "world");
   request.AddHeader("header", "value");
   request.AddFile("file", path);
   var response = client.Post(request);
   var content = response.Content; // Raw content as string
   var response2 = client.Post<Person>(request);
   var name = response2.Data.Name;

Flurl.Http

It is a newer library sporting a fluent API, testing helpers, uses HttpClient under the hood, and is portable. It is available via NuGet.

    using Flurl.Http;

  • POST

      var responseString = await "http://www.example.com/recepticle.aspx"
      .PostUrlEncodedAsync(new { thing1 = "hello", thing2 = "world" })
      .ReceiveString();

  • GET

      var responseString = await "http://www.example.com/recepticle.aspx"
      .GetStringAsync();

Method C: HttpWebRequest (not recommended for new work)

Available in: .NET Framework 1.1+, .NET Standard 2.0+, .NET Core 1.0+. In .NET Core, it is mostly for compatibility -- it wraps HttpClient, is less performant, and won't get new features.

using System.Net;
using System.Text;  // For class Encoding
using System.IO;    // For StreamReader

  • POST

      var request = (HttpWebRequest)WebRequest.Create("http://www.example.com/recepticle.aspx");

  var postData = "thing1=" + Uri.EscapeDataString("hello");
      postData += "&thing2=" + Uri.EscapeDataString("world");
  var data = Encoding.ASCII.GetBytes(postData);

  request.Method = "POST";
  request.ContentType = "application/x-www-form-urlencoded";
  request.ContentLength = data.Length;

  using (var stream = request.GetRequestStream())
  {
      stream.Write(data, 0, data.Length);
  }

  var response = (HttpWebResponse)request.GetResponse();

  var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

  • GET

      var request = (HttpWebRequest)WebRequest.Create("http://www.example.com/recepticle.aspx");

  var response = (HttpWebResponse)request.GetResponse();

  var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

Method D: WebClient (Not recommended for new work)

This is a wrapper around HttpWebRequest. Compare with HttpClient.

Available in: .NET Framework 1.1+, NET Standard 2.0+, and .NET Core 2.0+.

In some circumstances (.NET Framework 4.5-4.8), if you need to do a HTTP request synchronously, WebClient can still be used.

using System.Net;
using System.Collections.Specialized;

  • POST

      using (var client = new WebClient())
  {
      var values = new NameValueCollection();
      values["thing1"] = "hello";
      values["thing2"] = "world";

      var response = client.UploadValues("http://www.example.com/recepticle.aspx", values);

      var responseString = Encoding.Default.GetString(response);
  }

  • GET

      using (var client = new WebClient())
  {
      var responseString = client.DownloadString("http://www.example.com/recepticle.aspx");
  }

MSDN has a sample.

using System;
using System.IO;
using System.Net;
using System.Text;

namespace Examples.System.Net
{
    public class WebRequestPostExample
    {
        public static void Main()
        {
            // Create a request using a URL that can receive a post. 
            WebRequest request = WebRequest.Create("http://www.contoso.com/PostAccepter.aspx");
            // Set the Method property of the request to POST.
            request.Method = "POST";
            // Create POST data and convert it to a byte array.
            string postData = "This is a test that posts this string to a Web server.";
            byte[] byteArray = Encoding.UTF8.GetBytes(postData);
            // Set the ContentType property of the WebRequest.
            request.ContentType = "application/x-www-form-urlencoded";
            // Set the ContentLength property of the WebRequest.
            request.ContentLength = byteArray.Length;
            // Get the request stream.
            Stream dataStream = request.GetRequestStream();
            // Write the data to the request stream.
            dataStream.Write(byteArray, 0, byteArray.Length);
            // Close the Stream object.
            dataStream.Close();
            // Get the response.
            WebResponse response = request.GetResponse();
            // Display the status.
            Console.WriteLine(((HttpWebResponse)response).StatusDescription);
            // Get the stream containing content returned by the server.
            dataStream = response.GetResponseStream();
            // Open the stream using a StreamReader for easy access.
            StreamReader reader = new StreamReader(dataStream);
            // Read the content.
            string responseFromServer = reader.ReadToEnd();
            // Display the content.
            Console.WriteLine(responseFromServer);
            // Clean up the streams.
            reader.Close();
            dataStream.Close();
            response.Close();
        }
    }
}

Simple GET request

using System.Net;

...

using (var wb = new WebClient())
{
    var response = wb.DownloadString(url);
}

Simple POST request

using System.Net;
using System.Collections.Specialized;

...

using (var wb = new WebClient())
{
    var data = new NameValueCollection();
    data["username"] = "myUser";
    data["password"] = "myPassword";

    var response = wb.UploadValues(url, "POST", data);
    string responseInString = Encoding.UTF8.GetString(response);
}

Tags:

C#

.Net

Post

Httprequest

Httpwebrequest

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