如何定义早期绑定实体?

我正在尝试编译 this 代码示例。

它依赖于SystemUser:

                    // Now make an SDK call with the organization service proxy.
                // Display information about the logged on user.
                Guid userid = ((WhoAmIResponse)organizationProxy.Execute(
                    new WhoAmIRequest())).UserId;
                SystemUser systemUser = organizationProxy.Retrieve("systemuser", userid,
                    new ColumnSet(new string[] { "firstname", "lastname" })).ToEntity<SystemUser>();
                Console.WriteLine("Logged on user is {0} {1}.",
                    systemUser.FirstName, systemUser.LastName);

但是SystemUser是一个早期绑定的实体,不是吗?