Example.cs

var fb = new FacebookClient("access_token");

var result = fb.Get<FBUser1>("/me");

string name = result.Name;

FBUser1.cs

public class FBUser1 {
   public string name { get; set; }
   public string first_name { get; set; }
}

FBUser2.cs

public class FBUser2 {
   [DataMember(Name="name")]
   public string Name { get; set; }
   [DataMember(Name="first_name")]
   public string FirstName { get; set; }
}