How make an HTTP request in C# [duplicate]

I would highly recommend using the new HttpClient.

Please read the notes at the bottom of this answer

Excerpt from MSDN.

static async void Main()
{

    // Create a New HttpClient object.
    HttpClient client = new HttpClient();

    // Call asynchronous network methods in a try/catch block to handle exceptions
    try 
    {
       HttpResponseMessage response = await client.GetAsync("http://www.contoso.com/");
       response.EnsureSuccessStatusCode();
       string responseBody = await response.Content.ReadAsStringAsync();
       // Above three lines can be replaced with new helper method below
       // string responseBody = await client.GetStringAsync(uri);

       Console.WriteLine(responseBody);
    }  
    catch(HttpRequestException e)
    {
       Console.WriteLine("\nException Caught!");    
       Console.WriteLine("Message :{0} ",e.Message);
    }

    // Need to call dispose on the HttpClient object
    // when done using it, so the app doesn't leak resources
    client.Dispose(true);
 }

Since this answer was originally written there are some caveats about using HttpClient. (TLDR; it should be a singleton)

Using HttpClient As It Was Intended (Because You’re Not)

What is the overhead of creating a new HttpClient per call in a WebAPI client?

YOU'RE USING HTTPCLIENT WRONG AND IT IS DESTABILIZING YOUR SOFTWARE

Use HttpWebRequest E.g.

HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://www.google.com");
// access req.Headers to get/set header values before calling GetResponse. 
// req.CookieContainer allows you access cookies.

var response = req.GetResponse();
string webcontent;
using (var strm = new StreamReader(response.GetResponseStream()))
{
    webcontent = strm.ReadToEnd();
}

You can set headers/cookies on request by accessing Headers and CookieContainer properties of request object. You can also access various properties of response object to get various values.