c# - 为什么在 MassTransit 中强烈推荐消息契约接口(interface)？

Question

MassTransit 声明我们应该为消息契约使用接口(interface):

It is strongly suggested to use interfaces for message contracts, based on experience over several years with varying levels of developer experience. MassTransit will create dynamic interface implementations for the messages, ensuring a clean separation of the message contract from the consumer.

来源:文档 » 使用 MassTransit » Creating a message contract

使用 POCO DTO 而不是接口(interface)的缺点是什么？在使用 MassTransit 进行消息传递的上下文中，接口(interface)相对于类的明显优势是什么？

另一方面，NServiceBus 适用于 POCO，确保不使用域对象等内部类是有意义的，请参见下文。

来源:NServiceBus » Messaging » Messages, Events and Commands

When creating messages one should follow the following guidelines:

• Messages should be simple POCO objects.
• Messages should be as small as possible.
• Messages should satisfy a Single Responsibility Principle.
• Classes used for other purposes (e.g. domain objects, data access objects and UI binding objects) should not be used as messages.

Answer 1

虽然与 MassTransit 没有直接关系，但我会说原因是封装。使用 setter 创建一个简单的 POCO，但将其传递到 promise 仅 getter 的接口(interface)后面，将数据封装在 DTO 中。

public class Program
{
    static void Main(string[] args)
    {
        User user = new User()
        {
            Username = "user99"
        };

        Account account = new Account(user);
    }
}

public interface IUser
{
    string Username { get; }
}

public class User : IUser
{
    public string Username { get; set; }
}

public class Account
{
    private IUser user;

    //Currently used in main
    public Account(User user)
    {
        user.Username = ""; //This is allowed            
        this.user = user;
    }

    //But consider this ctor
    public Account(IUser user)
    {
        //user.Username = ""; //Not allowed
        this.user = user;
    }

    ...
}