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如何将泛型配置文件与Automapper和Asp.Net核心依赖注入一起使用

automapper .net-core asp.net-core c#

Jenan · 技术社区 · 6 年前

我要创建.Net核心类库,该类库将包含以下扩展方法:

public static class MyServiceExtensions
    {
        public static IServiceCollection AddMyService<TUserDto, TUserDtoKey, TUser, TUserKey>(this IServiceCollection services)
            where TUserDto : UserDto<TUserDtoKey>
            where TUser : User<TUserKey>
        {
            services.AddAutoMapper(config =>
            {
                config.AddProfile<UserMappingProfile<TUserDto, TUserDtoKey, TUser, TUserKey>>();
            });

            return services;
        }
    }

我有以下自动应用程序配置文件:

public class UserMappingProfile<TUserDto, TUserDtoKey, TUser, TUserKey> : Profile 
        where TUserDto : UserDto<TUserDtoKey>
        where TUser : User<TUserKey>
    {
        public UserMappingProfile()
        {
            CreateMap<TUserDto, TUser>(MemberList.Destination)
                .ForMember(x => x.Id, opts => opts.MapFrom(x => x.UserId));

            CreateMap<TUser, TUserDto > (MemberList.Source)
                .ForMember(x => x.UserId, opts => opts.MapFrom(x => x.Id));
        }
    }

这些实体:

public class UserDto<TKey>
    {
        public TKey UserId { get; set; }

        public string UserName { get; set; }
    }

public class User<TKey>
    {
        public TKey Id { get; set; }

        public string UserName { get; set; }
    }

public class MyUser : User<int>
    {
        public string Email { get; set; }
    }

public class MyUserDto : UserDto<int>
    {
        public string Email { get; set; }
    }

如果我想这样使用它:

services.AddMyService<MyUserDto, int, MyUser, int>();

我得到这个错误:

GenericMapping.Services.Mapping.UserMappingProfile 4[TUserDto,TUserDtoKey,TUser,TUserKey] because Type.ContainsGenericParameters is true. at System.RuntimeType.CreateInstanceCheckThis() at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean wrapExceptions, Boolean skipCheckThis, Boolean fillCache) at System.Activator.CreateInstance(Type type, Boolean nonPublic, Boolean wrapExceptions) at AutoMapper.Configuration.MapperConfigurationExpression.AddProfile(Type profileType) in C:\projects\automapper\src\AutoMapper\Configuration\MapperConfigurationExpression.cs:line 44 at AutoMapper.ServiceCollectionExtensions.<>c__DisplayClass10_0.<AddAutoMapperClasses>g__ConfigAction|4(IMapperConfigurationExpression cfg) in C:\projects\automapper-extensions-microsoft-dependencyinjectio\src\AutoMapper.Extensions.Microsoft.DependencyInjection\ServiceCollectionExtensions.cs:line 83 at AutoMapper.MapperConfiguration.Build(Action C: \projects\automapper\src\automapper\mappenconfiguration.cs:第307行 AutoMapper.ServiceCollectionExtensions.AddAutoMapperClasses(IServiceCollection 1 additionalInitAction, IEnumerable 1个 C: \projects\automapper extensions microsoft dependencyinjectio\src\automapper.extensions.microsoft.DependencyInjection\ServiceCollectionExtensions.cs:line 89在服务)中 C: \Projects\GenericMapping\GenericMapping.Services\Extensions\myserviceeextensions.cs:line 服务)在C:\项目\常规应用程序\常规应用程序\启动.cs:line中 33}

我怎样才能解决这个问题?

1 回复 | 直到 6 年前

Adam Simon 6 年前

问题的根本原因是扩展方法。此方法扫描程序集以查找配置文件(和其他自动应用程序组件)并注册图像使用找到的配置的DI容器中的组件。(我建议你看看 its sources

你得到例外是因为 添加自动应用程序 用户映射配置文件 类,但不知道如何实例化它,因为它有4个开放类型参数。

public abstract class UserMappingProfile<TUserDto, TUserDtoKey, TUser, TUserKey> : Profile
    where TUserDto : UserDto<TUserDtoKey>
    where TUser : User<TUserKey>
{
    public UserMappingProfile()
    {
        CreateMap<TUserDto, TUser>(MemberList.Destination)
            .ForMember(x => x.Id, opts => opts.MapFrom(x => x.UserId));

        CreateMap<TUser, TUserDto>(MemberList.Source)
            .ForMember(x => x.UserId, opts => opts.MapFrom(x => x.Id));
    }
}

public class UserMappingProfile : UserMappingProfile<MyUserDto, int, MyUser, int> { }

现在你不需要 MyService扩展 services.AddAutoMapper() 呼叫后,您的配置将自动获取。

添加自动应用程序 因为它只被调用一次。而不是扫描程序集类,您可以提供自己的注册逻辑。使用生成器模式的示例:

public class UserMappingProfile<TUserDto, TUserDtoKey, TUser, TUserKey> : Profile
    where TUserDto : UserDto<TUserDtoKey>
    where TUser : User<TUserKey>
{
    public UserMappingProfile()
    {
        CreateMap<TUserDto, TUser>(MemberList.Destination)
            .ForMember(x => x.Id, opts => opts.MapFrom(x => x.UserId));

        CreateMap<TUser, TUserDto>(MemberList.Source)
            .ForMember(x => x.UserId, opts => opts.MapFrom(x => x.Id));
    }
}

public interface IMapperConfigurationBuilder
{
    IMapperConfigurationBuilder UseProfile<TUserDto, TUserDtoKey, TUser, TUserKey>()
        where TUserDto : UserDto<TUserDtoKey>
        where TUser : User<TUserKey>;
}

public static class MyServiceExtensions
{
    private class MapperConfigurationBuilder : IMapperConfigurationBuilder
    {
        public HashSet<Type> ProfileTypes { get; } = new HashSet<Type>();

        public IMapperConfigurationBuilder UseProfile<TUserDto, TUserDtoKey, TUser, TUserKey>()
            where TUserDto : UserDto<TUserDtoKey>
            where TUser : User<TUserKey>
        {
            ProfileTypes.Add(typeof(UserMappingProfile<TUserDto, TUserDtoKey, TUser, TUserKey>));
            return this;
        }
    }

    public static IMapperConfigurationBuilder AddMyMapper(this IServiceCollection services)
    {
        var builder = new MapperConfigurationBuilder();

        services.AddSingleton<IConfigurationProvider>(sp => new MapperConfiguration(cfg =>
        {
            foreach (var profileType in builder.ProfileTypes)
                cfg.AddProfile(profileType);
        }));

        services.AddScoped<IMapper>(sp => new Mapper(sp.GetRequiredService<IConfigurationProvider>(), sp.GetService));
        return builder;
    }
}

然后映射配置文件注册将如下所示:

services.AddMyMapper()
    .UseProfile<MyUserDto, int, MyUser, int>();