.NET 6 EF项目Program.cs中AutoMapper依赖注入异常求助

异常信息 #

已触发异常：CLR/System.AggregateException
在Microsoft.Extensions.DependencyInjection.dll中发生未处理的System.AggregateException类型异常：‘部分服务无法构造’
已找到内部异常，可在变量窗口查看$exception获取更多详情。
最内层异常：System.InvalidOperationException : 尝试激活'ApplicationAdmin.EntityFrameworkLayer.Services.ApplicationService'时，无法解析'AutoMapper.Mapper'类型的服务。

调用栈信息：
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteFactory.CreateArgumentCallSites(Type implementationType, CallSiteChain callSiteChain, ParameterInfo[] parameters, Boolean throwIfCallSiteNotFound)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteFactory.CreateConstructorCallSite(ResultCache lifetime, Type serviceType, Type implementationType, CallSiteChain callSiteChain)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteFactory.TryCreateExact(ServiceDescriptor descriptor, Type serviceType, CallSiteChain callSiteChain, Int32 slot)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteFactory.GetCallSite(ServiceDescriptor descriptor, CallSiteChain callSiteChain)
at Microsoft.Extensions.DependencyInjection.ServiceProvider.ValidateService(ServiceDescriptor descriptor)

相关代码 #

Program.cs #

using ApplicationAdmin.BusinessLayer.Interfaces;
using ApplicationAdmin.BusinessLayer.Services;
using ApplicationAdmin.EntityFrameworkLayer.Data.Contexts;
using ApplicationAdmin.EntityFrameworkLayer.Interfaces;
using ApplicationAdmin.EntityFrameworkLayer.Services;
using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);
ConfigurationManager config = builder.Configuration;

// Add services to the container.

builder.Services.AddAutoMapper(AppDomain.CurrentDomain.GetAssemblies());
builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddDbContext<dbContext>(options => options.UseSqlServer(config.GetConnectionString("default")));
// builder.Services.AddAutoMapper(config => config.AddProfile<ApplicationProfile>());
// builder.Services.AddAutoMapper(config => config.AddProfile<FieldProfile>());
builder.Services.AddScoped<IApplicationService,ApplicationService>();
builder.Services.AddScoped<IFieldService,FieldService>();
builder.Services.AddScoped<IPageService,PageService>();
builder.Services.AddScoped<ISectionService,SectionService>();
builder.Services.AddScoped<ISubsectionService,SubsectionService>();
builder.Services.AddScoped<IApplicationBLService,ApplicationBLService>();
builder.Services.AddScoped<IFieldBLService,FieldBLService>();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

ApplicationService.cs #

using ApplicationAdmin.EntityFrameworkLayer.Data.Models;
using ApplicationAdmin.EntityFrameworkLayer.Data.Contexts;
using ApplicationAdmin.BusinessLayer.DataModels.Application;
using ApplicationAdmin.EntityFrameworkLayer.Interfaces;
using Microsoft.EntityFrameworkCore;
using ApplicationAdmin.Helper;
using AutoMapper;

namespace ApplicationAdmin.EntityFrameworkLayer.Services;

public class ApplicationService : IApplicationService
{
    private dbContext _dbContext;
    private Mapper _mapper;

    public ApplicationService (dbContext dbContext, Mapper mapper)
    {
        _dbContext = dbContext;
        _mapper = mapper;
    }

    public async Task<List<Application>> Get(GetApplicationRequest request, CancellationToken xlT)
    {
        Guid guidApplicationId = Guid.Empty;
        Guid.TryParse(request.ApplicationId, out guidApplicationId); 

        return await _dbContext.Applications
            .Where(i => 
                i.ApplicationId == (request.ApplicationId == null ? i.ApplicationId : guidApplicationId) && 
                i.CreatedById == (request.CreatedById ?? i.CreatedById) && 
                i.CreatedOnUtc == (request.CreatedOnUtc ?? i.CreatedOnUtc) && 
                EF.Functions.Like(i.Description,(StringConverter.ConvertToLike(request.Description) ?? i.Description)) && 
                i.IsEnabled == (request.IsEnabled ?? i.IsEnabled) && 
                i.UpdatedById == (request.UpdatedById ?? i.UpdatedById) && 
                i.UpdatedOnUtc == (request.UpdatedOnUtc ?? i.UpdatedOnUtc)
            )
            .ToListAsync(xlT);
    }

    public async Task<List<Application>> Post(List<PostApplicationRequest> requests, bool saveNow, CancellationToken xlT)
    {
        List<Application> applications = new List<Application>();

        foreach(PostApplicationRequest request in requests)
        {
            Application application = new Application()
            {
                ApplicationId = Guid.NewGuid(),
                Description = request.Description, 
                IsEnabled = request.IsEnabled, 
                CreatedById = request.CreatedById, 
                CreatedOnUtc = DateTime.UtcNow
            };

            applications.Add(application);
        }

        _dbContext.AddRange(applications);

        if(saveNow)
        {
            await _dbContext.SaveChangesAsync(xlT);            
        }

        return applications;
    }

    public async Task<List<Application>> Put(PutApplicationRequest request, bool saveNow, CancellationToken xlT)
    {
        List<Application> applications = await Get(_mapper.Map<GetApplicationRequest>(request), xlT);

        foreach(Application application in applications)
        {
            application.Description = (request.Description ?? application.Description); 
            application.IsEnabled = (request.IsEnabled ?? application.IsEnabled); 
            
            if(_dbContext.ChangeTracker.HasChanges())
            {
                application.UpdatedById = request.UpdatedById;
                application.UpdatedOnUtc = DateTime.UtcNow;
            };
        };

        if(saveNow && _dbContext.ChangeTracker.HasChanges())
        {
            await _dbContext.SaveChangesAsync(xlT);            
        }

        return applications;
    }
}

IApplicationService.cs #

using ApplicationAdmin.EntityFrameworkLayer.Data.Models;
using ApplicationAdmin.BusinessLayer.DataModels.Application;

namespace ApplicationAdmin.EntityFrameworkLayer.Interfaces;
public interface IApplicationService
{
    public Task<List<Application>> Get(GetApplicationRequest request, CancellationToken xlT);
    public Task<List<Application>> Put(PutApplicationRequest request, bool saveNow, CancellationToken xlT);
    public Task<List<Application>> Post(List<PostApplicationRequest> requests, bool saveNow, CancellationToken xlT);
}

解决方案 #

1. 修改构造函数依赖类型 #

AutoMapper在依赖注入容器中注册的是IMapper接口，而非具体的Mapper实现类。修改ApplicationService代码：

// 替换原私有字段类型
private IMapper _mapper;

// 替换构造函数参数类型
public ApplicationService (dbContext dbContext, IMapper mapper)
{
    _dbContext = dbContext;
    _mapper = mapper;
}

2. 确保AutoMapper配置正确 #

如果项目中有自定义的AutoMapper Profile（比如注释掉的ApplicationProfile、FieldProfile），可以合并注册代码：

// 替换原AddAutoMapper调用（二选一即可）
// 方式1：指定Profile类型注册
builder.Services.AddAutoMapper(typeof(ApplicationProfile), typeof(FieldProfile));
// 方式2：扫描所有程序集自动发现Profile
// builder.Services.AddAutoMapper(AppDomain.CurrentDomain.GetAssemblies());

完成以上修改后，依赖注入容器就能正确解析IMapper服务，解决服务构造失败的问题。

内容的提问来源于stack exchange，提问作者John Hedge