从NET Core上的Automapper Value Resolver读取声明 [英] Read Claims from Automapper Value Resolver on NET Core

问题描述

我有一个自动映射器个人资料，如下所示:

I have a Automapper Mapping Profile like this:

CreateMap<MyViewModel, MyDto>()
.ForMember(s => s.MyProperty, opt => opt.ResolveUsing<CustomResolver>());

这是我的 CustomResolver 类(旨在通过Claims解决值):

And this is my CustomResolver class (that aims to solve a value through the Claims):

public class CustomResolver : IValueResolver<object, object, string>
{
    private readonly HttpContext _context;

    public CompanyResolver(IHttpContextAccessor httpContextAccessor)
    {
        _context = httpContextAccessor.HttpContext;
    }

    public string Resolve(object source, object destination, string destMember, ResolutionContext context)
    {
        return "I will return here a value from Claims inside _context";
    }
}

很明显，在我的 Startup 类中，我注册了我的服务:

Obviously, on my Startup class I registered my Services:

services.AddTransient<IHttpContextAccessor, HttpContextAccessor>();

但是，总是，我从Automapper收到此异常:

But, Always, I received this exception from Automapper:

没有为此对象定义无参数的构造函数.

No parameterless constructor defined for this object.

但是，正是因为我想接收IHttpContextAccesor实例，我才希望该请求通过带有参数的构造函数(CustomResolver).

But, precisely, I want the request to go through the constructor (CustomResolver) with parameters because I want to receive IHttpContextAccesor instance.

怎么了?为什么NET Core无法注入接口?

What's wrong? Why is NET Core not capable of injecting the interface?

推荐答案

我通过更改以下内容解决了问题:

var automapperConfig = new MapperConfiguration(configuration =>
{
    configuration.AddProfile(new MyProfile());
});

var autoMapper = automapperConfig.CreateMapper();
services.AddSingleton(autoMapper);

对此:

services.AddAutoMapper(configuration =>
{
    configuration.AddProfile(new MyProfile());
});

我不明白100％的原因，但我想我们不应该将Automapper添加为Singleton

I do not understand 100% the reason but I guess we should not add Automapper as Singleton

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