AutoMapper：如果源中不存在该属性，则保留目标值

Question

我尝试了很多搜索，然后尝试了其他选项，但似乎没有任何效果。

我正在使用ASP.net Identity 2.0，并且具有UpdateProfileViewModel。更新用户信息时，我想将UpdateProfileViewModel映射到ApplicationUser（即，身份模型）。但是我想保留这些值，我是从用户数据库中获得的。即用户名和电子邮件地址，不需要更改。

我试着做：

Mapper.CreateMap<UpdateProfileViewModel, ApplicationUser>()
.ForMember(dest => dest.Email, opt => opt.Ignore());

但是映射后我仍然将Email设置为null：

var user = await UserManager.FindByIdAsync(User.Identity.GetUserId());
user = Mapper.Map<UpdateProfileViewModel, ApplicationUser>(model);

我也试过了，但是没有用：

public static IMappingExpression<TSource, TDestination> IgnoreAllNonExisting<TSource, TDestination>(this IMappingExpression<TSource, TDestination> expression)
    {
        var sourceType = typeof(TSource);
        var destinationType = typeof(TDestination);
        var existingMaps = Mapper.GetAllTypeMaps().First(x => x.SourceType.Equals(sourceType) && x.DestinationType.Equals(destinationType));
        foreach (var property in existingMaps.GetUnmappedPropertyNames())
        {
            expression.ForMember(property, opt => opt.Ignore());
        }
        return expression;
    }

然后：

 Mapper.CreateMap<UpdateProfileViewModel, ApplicationUser>()
.IgnoreAllNonExisting();

Answer 1

您需要做的是在源类型和目标类型之间创建映射：

Mapper.CreateMap<UpdateProfileViewModel, ApplicationUser>();

然后执行映射：

UpdateProfileViewModel viewModel = ... this comes from your view, probably bound
ApplicationUser user = await UserManager.FindByIdAsync(User.Identity.GetUserId());
Mapper.Map(viewModel, user);

// at this stage the user domain model will only have the properties present
// in the view model updated. All the other properties will remain unchanged
// You could now go ahead and persist the updated 'user' domain model in your
// datastore