WebClient vs. HttpClient - Async request

I have this very simple WebApi method:

[HttpGet]
public IHttpActionResult Foo()
{
    Thread.Sleep(3000);
    return Ok("Bar");
}

      

        
        
        
      

    

And I have two methods in a console application that call it:

async Task UsingWebClient()
{
    Task<string> task = new WebClient().DownloadStringTaskAsync (new Uri ("http://localhost.fiddler:63710/api/producttype/Foo"));
    Console.WriteLine("WebClient - Before calling wait");
    string result = await task;
    Console.WriteLine("WebClient - After calling wait");
}

async Task UsingHttpClient()
{
    Task<string> task = new HttpClient().GetStringAsync (new Uri ("http://localhost.fiddler:63710/api/producttype/Foo"));
    Console.WriteLine("HttpClient - Before calling wait");
    string result = await task;
    Console.WriteLine("HttpClient - After calling wait");
}

      

        
        
        
      

    

And I am calling these methods from LinqPad like this:

async Task Main()
{
    await UsingWebClient();
    await UsingHttpClient();
}

      

        
        
        
      

    

I was tracking traffic using Fiddler and I noticed that:

• when using WebClient, the web api request is executed immediately and then execution continues to Console.WriteLine ("WebClient - Before call wait");
• when using HttpClient, the request to the web api is not executed until the call is waiting for the task;

I am trying to understand why the request is not immediately executed when using the HttpClient. Can anyone point me in the right direction?

This is not a duplicate question. I'm not looking for a reason to pick one option over the other - I'll be using HttpClient. I would like to know specifically why the request is generated at a later stage when using the HttpClient.

Thanks David