AutoMapper 实体到 Dto 转换：映射类型错误

Question

我的实体中有不应该暴露给外部的数据。所以我想通过将实体映射到 dto 来导出实体。我收到的数据类型为 IList<Article>。我需要将其转换为 IList<ArticleBasicDto> 但是当我尝试这样做时出现错误。

我尝试用这种方式导出IList<ArticleBasicDto>作为目标，但是失败了。刚刚学习，没有达到效果，怎么办？

我这样做的原因是文章中关于用户实体的信息太多了。另外，JSON输出中的Article Object中有一个Category字段，属于该Category的文章会在该字段中再次列出。我正在尝试使用 Dto 来摆脱这些不必要的字段。

错误信息

An unhandled exception occurred while processing the request. AutoMapperMappingException: Missing type map configuration or unsupported mapping.

Mapping types: Article -> ArticleBasicDto Blog.Entities.Concrete.Article -> Blog.Entities.Dtos.ArticleBasicDto lambda_method178(Closure , Article , ArticleBasicDto , ResolutionContext )

AutoMapperMappingException: Error mapping types.

Mapping types: IList1 -> IList1 System.Collections.Generic.IList1[[Blog.Entities.Concrete.Article, Blog.Entities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] -> System.Collections.Generic.IList1[[Blog.Entities.Dtos.ArticleBasicDto, Blog.Entities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] lambda_method177(Closure , IList , IList , ResolutionContext )

映射器简介

namespace Blog.Business.AutoMapper.Profiles
{
    public class ArticleProfile : Profile
    {
        public ArticleProfile()
        {
           CreateMap<Article, ArticleBasicDto>().ForMember(dest => dest.Category, opt => opt.MapFrom(x => x.Category)).ForMember(dest => dest.User,
                opt => opt.MapFrom(x => x.User));
        }
    }
}

Dtos

namespace Blog.Entities.Dtos
{
    public class ArticleBasicDto
    {
        public string Title { get; set; }
        public string Content { get; set; }
        public string Thumbnail { get; set; }
        public DateTime Date { get; set; }
        public int ViewsCount { get; set; } = 0;
        public int CommentCount { get; set; } = 0;
        public UserBasicDto User { get; set; }
        public CategoryBasicDto Category { get; set; }
    }
}

namespace Blog.Entities.Dtos
{
    public class CategoryBasicDto
    {
        public string Name { get; set; }
        public string Description { get; set; }
        public string Slug { get; set; }
    }
}

namespace Blog.Entities.Dtos
{
    public class UserBasicDto
    {
        public string Email { get; set; }
        public string Username { get; set; }
        public string Picture { get; set; }
    }
}

经理GetAllBasic方法

public async Task<IDataResult<ArticleBasicListDto>> GetAllBasic()
        {
            var results = await _unitOfWork.Articles.GetAllAsync();
            var mapping = _mapper.Map<IList<ArticleBasicDto>>(results);
            return new DataResult<ArticleBasicListDto>(ResultStatus.Success, new ArticleBasicListDto()
            {
                Articles = mapping,
            });
        }

MVC 层 - Startup.cs

namespace Blog.MVC
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews().AddRazorRuntimeCompilation().AddNewtonsoftJson(opt => opt.SerializerSettings.ReferenceLoopHandling
                = Newtonsoft.Json.ReferenceLoopHandling.Ignore);
            services.AddAutoMapper(typeof(Startup));
            services.LoadMyServices();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseStatusCodePages();
            }

            app.UseStaticFiles();

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapAreaControllerRoute(
                    name: "Admin",
                    areaName: "Admin",
                    pattern: "Admin/{controller=Home}/{action=Index}/{id?}"
                );
                endpoints.MapDefaultControllerRoute();
                endpoints.MapControllers();
            });
        }
    }
}

Answer 1

要解决此问题，您必须将 startup class 替换为 ArticleProfile，如下所示 services.AddAutoMapper(typeof(ArticleProfile ));

它将解决您的问题。

Answer 2

您需要为用户和类别定义映射

CreateMap<User,CategoryBasicDto>();
CreateMap<Category,CategoryBasicDto>();