Is there any class, library or some piece of code which will help me to upload files with HTTPWebrequest?
Edit 2:
I do not
Check out the MyToolkit library:
var request = new HttpPostRequest("http://www.server.com");
request.Data.Add("name", "value"); // POST data
request.Files.Add(new HttpPostFile("name", "file.jpg", "path/to/file.jpg"));
await Http.PostAsync(request, OnRequestFinished);
http://mytoolkit.codeplex.com/wikipage?title=Http