DotNet Core 3.1 Web API + AutoMapper：mapper.map 方法出错

Question

我在 ASP.Net Core 3 Web API 项目中使用 Nuget 包 AutoMapper.Extensions.Microsoft.DependencyInjection 版本 7.0.0。

当我使用 Map() 方法时...

IEnumerable<SchoolForListDto> schoolsToReturn = _mapper<IEnumerable<School>, IEnumerable<SchoolForListDto>>.Map(schools);

...我收到以下错误消息：

Type arguments in method IMapper.Map<TDestination>(object) cannot be inferred from the usage. Try specifying the type arguments explicitly.

完整代码：

Models/Holder.cs

using System;
using System.Collections.Generic;

namespace SchoolApi.Models
{
    public class Holder
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public DateTime Created { get; set; }
        public DateTime Updated { get; set; }
        public virtual ICollection<School> Schools { get; set; }
    }
}

Models/School.cs

using System;
using System.Collections.Generic;

namespace SchoolApi.Models
{
    public class School
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public string PhoneNumber { get; set; }
        public string Email { get; set; }
        public string WebSite { get; set; }
        public string Address { get; set; }
        public string HolderId { get; set; }
        public DateTime Created { get; set; }
        public DateTime Updated { get; set; }
        public virtual Holder Holder { get; set; }
    }
}

Data/DataContext.cs

using Microsoft.EntityFrameworkCore;
using SchoolApi.Models;

namespace SchoolApi.Data
{
    public class DataContext : DbContext
    {
        public DbSet<Holder> Holders { get; set; }
        public DbSet<School> Schools { get; set; }

        public DataContext(DbContextOptions<DataContext> options)
            : base(options) { }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            base.OnModelCreating(builder);
        }
    }
}

Data/IGenericRepository

using System.Collections.Generic;
using System.Threading.Tasks;

namespace SchoolApi.Data
{
    public interface IGenericRepository<TEntity> where TEntity : class
    {
        void Add(TEntity entity);
        void Delete(TEntity entity);
        Task<TEntity> Get(object id);
        Task<IEnumerable<TEntity>> GetAll();
        Task<bool> SaveAll();
        void Update(TEntity entity);
    }
}

Data/GenericRepository

using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

namespace SchoolApi.Data
{
    public class GenericRepository<TEntity> : IGenericRepository<TEntity> where TEntity : class
    {
        private readonly DataContext _dataContext;
        private readonly string _entityName = typeof(TEntity).FullName;
        public GenericRepository(DataContext dataContext)
        {
            _dataContext = dataContext;
        }

        public void Add(TEntity entity)
        {
            _dataContext.Set<TEntity>().Add(entity);
        }

        public void Delete(TEntity entity)
        {
            _dataContext.Set<TEntity>().Remove(entity);
        }

        public async Task<TEntity> Get(object id)
        {
            TEntity entity = await _dataContext.Set<TEntity>().FindAsync(id);
            return entity;
        }

        public async Task<IEnumerable<TEntity>> GetAll()
        {
            IEnumerable<TEntity> entities = await _dataContext.Set<TEntity>().ToListAsync();
            return entities;
        }

        public async Task<bool> SaveAll()
        {
            int result = await _dataContext.SaveChangesAsync();
            return result > 0;
        }

        public void Update(TEntity entity)
        {
            _dataContext.Set<TEntity>().Update(entity);
        }
    }
}

Dtos/SchoolForListDto.cs

namespace SchoolApi.Dtos
{
    public class SchoolForListDto
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public string PhoneNumber { get; set; }
        public string Email { get; set; }
        public string HolderName { get; set; }
    }
}

Helpers/AutoMapperProfiles

using AutoMapper;
using SchoolApi.Dtos;
using SchoolApi.Models;

namespace SchoolApi.Helpers
{
    public class AutoMapperProfiles : Profile
    {
        public AutoMapperProfiles()
        {
            CreateMap<School, SchoolForListDto>()
                .ForMember(dest => dest.HolderName, opt => opt.MapFrom(src => src.Holder.Name));
        }
    }
}

Startup.cs

using AutoMapper;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using SchoolApi.Data;
using SchoolApi.Models;

namespace SchoolApi
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers()
                .AddNewtonsoftJson(options =>
                {
                    options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
                });

            services.AddCors();

            services.AddDbContext<DataContext>(options => options.UseLazyLoadingProxies().UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

            services.AddAutoMapper(typeof(Startup));

            services.AddScoped<IGenericRepository<School>, GenericRepository<School>>();
        }

        // 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.UseCors(x => x.AllowAnyOrigin().AllowAnyHeader().AllowAnyMethod());

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

Controllers/SchoolController.cs

using System.Collections.Generic;
using System.Threading.Tasks;
using AutoMapper;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using SchoolApi.Data;
using SchoolApi.Dtos;
using SchoolApi.Models;

namespace SchoolApi.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class SchoolController : ControllerBase
    {
        private readonly IGenericRepository<School> _repository;
        private readonly IMapper _mapper;
        private readonly ILogger<SchoolController> _logger;

        public SchoolController(IGenericRepository<School> repository, IMapper mapper, ILogger<SchoolController> logger)
        {
            _repository = repository;
            _mapper = mapper;
            _logger = logger;
        }

        [HttpGet]
        public async Task<IActionResult> GetAll()
        {
            IEnumerable<School> schools = await _repository.GetAll();
            // The error occurs on the following line
            IEnumerable<SchoolForListDto> schoolsToReturn = _mapper<IEnumerable<School>, IEnumerable<SchoolForListDto>>.Map(schools);
            return Ok(schoolsToReturn);
        }

        [HttpGet("{id}")]
        public async Task<IActionResult> Get([FromRoute] string id)
        {
            School school = await _repository.Get(id);
            SchoolForListDto schoolToReturn = _mapper.Map<SchoolForListDto>(school);
            return Ok(schoolToReturn);
        }
    }
}

这些是我正在使用的软件包： - AutoMapper.Extensions.Microsoft.DependencyInjection（版本 7.0.0） - Microsoft.AspNetCore.Mvc.NewtonsoftJson（版本 3.1.4） - Microsoft.EntityFrameworkCore（版本 3.1.4） - Microsoft.EntityFrameworkCore.设计（版本 3.1.4） - Microsoft.EntityFrameworkCore.代理（版本 3.1.4） - Microsoft.EntityFrameworkCore.关系型（版本 3.1.4） - Microsoft.EntityFrameworkCore.SqlServer（版本 3.1.4）

目标框架：DotNet Core 3.1 IDE: Visual Studio 代码所以：Windows 10 GitHub 存储库：https://github.com/jmcandia/SchoolApi

Answer 1

感谢@TimothyMacharia 的建议。它有效地帮助我解决了问题。

我更改了这段代码...

IEnumerable<SchoolForListDto> schoolsToReturn = _mapper<IEnumerable<School>, IEnumerable<SchoolForListDto>>.Map(schools);

...对于这个，它起作用了。

IEnumerable<SchoolForListDto> schoolsToReturn = _mapper.Map<IEnumerable<SchoolForListDto>>(schools);

DotNet Core 3.1 Web API + AutoMapper：mapper.map 方法出错

DotNet Core 3.1 Web API + AutoMapper: Error in mapper.map method

c#

automapper

.net-core

asp.net-core-webapi