如何使用通用配置文件与Automapper和Asp.Net核心依赖注入-Java 学习之路

我想创建.Net Core类库，它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Automapper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; }
    }

如果我尝试像这样使用它：

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

我收到此错误：

{System.ArgumentException：无法创建GenericMapping.Services.Mapping.UserMappingProfile4 [TUserDto，TUserDtoKey，TUser，TUserKey]的实例，因为Type.ContainsGenericParameters为true . 在System.RuntimeType.CreateInstanceCheckThis（）处于System.RuntimeType.CreateInstanceSlow（Boolean publicOnly，Boolean wrapExceptions，Boolean skipCheckThis，Boolean fillCache），位于AutoMapper.Configuration.MapperConfigurationExpression的System.Activator.CreateInstance（Type type，Boolean nonPublic，Boolean wrapExceptions） . AddProfile（Type profileType）位于C：\ projects \ _自动化器\ src \ AutoMapper \ Configuration \ MapperConfigurationExpression.cs：第44行的AutoMapper.ServiceCollectionExtensions . <> c__DisplayClass10_0 . <AddAutoMapperClasses> g__ConfigAction | 4（IMapperConfigurationExpression cfg）在C：\ projects \ automapper-extensions-microsoft-dependencyinjectio \ src \ AutoMapper.Extensions.Microsoft.DependencyInjection \ ServiceCollectionExtensions.cs：位于C：\ projects \ automapper \ src \ AutoMapper \ MapperConfiguration.cs中AutoMapper.MapperConfiguration.Build（Action1 configure）的第83行： AutoMapper.ServiceCollectionExtensions.AddAutoMapperClasses的第307行（IServiceCollection服务，Action1 additionalInitAction），IEnumerable1 assembliesToScan）在C：\ projects \ automapper-extensions-microsoft-dependencyinjectio \ src \ AutoMapper.Extensions.Microsoft.DependencyInjection \ ServiceCollectionExtensions.cs：第89行，GenericMapping.Services.Extensions.MyServiceExtensions.AddMyService [TUserDto，TUserDtoKey，TUser ，TUserKey]（IServiceCollection服务），位于C：\ Projects \ GenericMapping，GenericMapping \ Startup.cs中的C：：第33行

我该如何解决这个问题？

1 回答

您的问题的根本原因是AddAutoMapper扩展方法的错误使用 . 此方法扫描程序集以查找配置文件（和其他AutoMapper组件），并使用找到的配置在DI容器中注册IMapper组件 . （我建议你看一下its sources来了解究竟发生了什么 . ）

您得到异常，因为AddAutoMapper找到UserMappingProfile类，但不知道如何实例化它，因为它有4个打开类型参数 .

解决问题的最简单方法是使您的通用配置文件类成为抽象，并使用所需的类型参数对其进行子类化：

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> { }

现在您根本不需要MyServiceExtensions，只需 services.AddAutoMapper() 调用，您的配置将自动获取 .

但是，如果您坚持使用自己的扩展方法进行配置，则必须避免使用AddAutoMapper，因为它只打算调用一次 . 您可以提供自己的注册逻辑，而不是扫描Profile类的程序集 . 使用构建器模式的示例：

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>();

回复于 2024-04-28T07:32:43+08:00

如何使用通用配置文件与Automapper和Asp.Net核心依赖注入

1 回答

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