AutoMapper-为什么要覆盖整个对象? [英] AutoMapper - Why it is overwriting whole object?

问题描述

我不明白为什么它会覆盖我的整个对象.原因是我从db获得了User对象，我想从DTO分配新值.不仅仅是添加这些新值，而是创建具有新值但所有先前值都设置为null的新对象.

I don't understand why it's overwriting my whole object. The reason is that I get my User object from db an I want to assign new values from DTO. Instead of just adding those new values it's creating new object that has new values but all previous are set to null.

在这种情况下，我如何确保他将升级"我的对象，而不是创建新对象?

How can I make sure that in this case he will "upgrade" my object, not create new one?

/users/{id}-放置

// User has id, username, fullname
// UserPut has fullname
public HttpResponseMessage Put(int id, UserPut userPut)
{
    var user = _db.Users.SingleOrDefault(x => x.Id == id); // filled with properties

    Mapper.CreateMap<UserPut, User>();
    user = Mapper.Map<User>(userPut); // now it has only "fullname", everything else set to null

    // I can't save it to db because everything is set to null except "fullname"

    return Request.CreateResponse(HttpStatusCode.OK, user);
}

推荐答案

Mapper.Map具有一个重载，该重载带有一个源对象和一个目标对象.在这种情况下，Automapper将使用给定的目标对象，并且不会创建新对象.

The Mapper.Map has an overload which takes a source and a destination object. In this case Automapper will use the given destination object and does not create a new object.

因此您需要将Mapper.Map重写为:

Mapper.Map<UserPut, User>(userPut, user);

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