Does WebClient use KeepAlive?

Question

I need to issue around 50 HTTP requests to a single host (API calls). Performance is important, so I'd like to use HTTP KeepAlive's. Does WebClient support this?

Answer 1

It does on my machine, but I can't see that it's documented to. I'd certainly expect it to by default. The simplest way to tell is to run Wireshark (or Fiddler) and look at exactly what's going down the wire.

For example, this program:

using System;
using System.Net;

class Test
{    
    static void Main()
    {
        WebClient client = new WebClient();
        for (int i = 0; i < 50; i++)
        {
            string text = client.DownloadString("http://www.microsoft.com");
            Console.WriteLine(text.Length);
        }
    }
}

Generates a first request of:

GET / HTTP/1.1   
Host: www.microsoft.com    
Connection: Keep-Alive

Subsequence requests are just:

GET / HTTP/1.1
Host: www.microsoft.com

... presumably because once a connection is in KeepAlive mode, it's assumed it will stay that way.