Question

I like the HttpClient in ASP.NET Web API. Can I use it in 3.5 or 2.0. I mean in any .NET Framework application versions before 4.0. Actually, I have a ASP.NET Web API app in ASP.NET 4.0. I need to consume this app from a device built in 3.5 framework. I know I can use WebClient/WebRequest, But It will be great If I can use HttpClient stuffs.

Answer 1

According to this,

WebAPI requires .net 4. You can’t use it on .net 3.5 (sp1 or not).

You also can’t use the preview releases for production code as you
don’t have a “go-live” license, so even if you could get it to work,
it wouldn’t be legal. You need to use at least the ASP.NET WebAPI Beta
to get a go-live license.

And according to this,

The HttpClient library was initially introduced in the “WCF REST
Starter Kit” project, so you can download it from there. This project
isn’t supported anymore (most of its functionality has either made it
into the framework or is now part of the Web API project), but the
HttpClient from there works quite well.