我正在开发一个web应用程序-承载在ASP.NET上的Blazor WebAssembly。我正在尝试从数据库中获取值(实体框架使用(。我在解决方案中使用Repository和UnitOfWork模式。所以，我面临这个错误：
An unhandled exception has occurred while executing the request.
System.InvalidOperationException: Unable to resolve service for type 'ReportApp.Core.Services.TaskService' while attempting to activate 'ReportApp.Server.Controllers.TaskController'.
at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, Boolean isDefaultParameterRequired)
at lambda_method8(Closure , IServiceProvider , Object[] )
at Microsoft.AspNetCore.Mvc.Controllers.ControllerActivatorProvider.<>c__DisplayClass4_0.<CreateActivator>b__0(ControllerContext controllerContext)
at Microsoft.AspNetCore.Mvc.Controllers.ControllerFactoryProvider.<>c__DisplayClass5_0.<CreateControllerFactory>g__CreateController|0(ControllerContext controllerContext)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
at Microsoft.AspNetCore.Builder.Extensions.MapWhenMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Builder.Extensions.MapMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
我的项目结构如下：
DbContext类：
public class ReportAppContext : DbContext
{
public DbSet<TaskEntity> Tasks { get; set; }
public DbSet<ReportEntity> Reports { get; set; }
public DbSet<EmployeeEntity> Employees { get; set; }
public ReportAppContext()
{
}
public ReportAppContext(DbContextOptions<ReportAppContext> options) : base(options)
{
}
}
Repository接口：
public interface ITaskRepository : IGenericRepository<TaskEntity>
{
}
public interface IGenericRepository<TEntity> where TEntity : class
{
Task<TEntity> GetByIdAsync(Int32 id);
Task InsertAsync(TEntity entity);
Task UpdateAsync(TEntity entity);
Task DeleteAsync(Int32 id);
Task<IEnumerable<TEntity>> GetAllAsync();
Task SaveAsync();
}
public class TaskRepository : ITaskRepository
{
private readonly ReportAppContext _context;
public TaskRepository(ReportAppContext context)
{
_context = context;
}
然后我有UnitOfWork模式：
public class UnitOfWork : ReportAppContext, IUnitOfWork
{
private readonly ITaskRepository _taskRepository;
服务器上的控制器：
[Route("api/[controller]")]
[ApiController]
public class TaskController : ControllerBase
{
private readonly TaskService _taskService;
public TaskController(TaskService taskService)
{
_taskService = taskService;
}
[HttpGet("get-all")]
public async Task<ActionResult<List<TaskDto>>> GetAllTasksAsync()
{
var result = await _taskService.GetAllAsync();
return Ok(result);
}
最后，Startup类配置：
public void ConfigureServices(IServiceCollection services)
{
var connection = Configuration.GetConnectionString("DefaultConnection");
services.AddDbContext<ReportAppContext>(options => options.UseSqlServer(connection));
services.AddCors();
services.AddServerSideBlazor().AddCircuitOptions(options => { options.DetailedErrors = true; });
services.AddControllersWithViews();
services.AddRazorPages();
}
// 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.UseWebAssemblyDebugging();
}
else
{
app.UseExceptionHandler("/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseBlazorFrameworkFiles();
app.UseStaticFiles();
app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapRazorPages();
endpoints.MapControllers();
endpoints.MapFallbackToFile("index.html");
});
}
我试着添加这个：
services.AddTransient<ITaskRepository, TaskRepository>();
AddScoped也是如此，但它没有改变任何。。。
但是在TaskController中注入的是TaskService，而不是TaskRepository。我认为您还需要注册TaskService(我假设TaskService使用TaskRepository。两者都可以注册为Scoped(。
services.AddTransient<ITaskRepository, TaskRepository>(); OR
services.AddScoped<ITaskRepository, TaskRepository>();
services.AddTransient<TaskService>(); OR
services.AddScoped<TaskService>();
scoped和transient之间的区别在于，当您将服务注册为transient时，每次解析时都会返回一个新实例，而scoped将在作用域期间返回相同的实例。
错误告诉您TaskService未注册，但您的控制器需要将其作为注入的服务。
在ConfigureServices中，尝试以下操作：
services.AddScoped<TaskService>(sp => {
// Build your Context Options
DbContextOptionsBuilder<ReportAppContext> optsBuilder = new DbContextOptionsBuilder<ReportAppContext>();
optsBuilder.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"));
// Build your context (using the options from the builder)
ReportAppContext ctx = new ReportAppContext(optsBuilder.options);
// Build your unit of work (and pass in the context)
UnitOfWork uow = new UnitOfWork(ctx);
// Build your service (and pass in the unit of work)
TaskService svc = new TaskService(uow)
// Return your Svc
return svc;
});
然后，您的控制器将收到一个完全配置的TaskService，可供使用。
如果您愿意，您可以依次将每个项目放入DI容器中，但UOW、Repository&上下文不需要在TaskService之外访问，所以这有点浪费时间。
只需创建如上所述配置的TaskService，这就是DI容器需要注入的全部内容。
我也遇到了同样的错误，但以上解决方案对我的情况没有帮助。当我有以下注册时，我意外地尝试注入具体类ReviewRepository而不是接口IReviewRepository：
services.AddScoped<IReviewRepository, ReviewRepository>();
以及以下消费代码：
private IReviewRepository _reviewRepository;
private IPokemonRepository _pokemonRepository;
private readonly IReviewerRepository _reviewerRepository;
private IMapper _mapper;
public ReviewController(ReviewRepository reviewRepository,
IMapper mapper,
IPokemonRepository pokemonRepository,
ReviewerRepository reviewerRepository)
{
_reviewRepository = reviewRepository;
_pokemonRepository = pokemonRepository;
_reviewerRepository = reviewerRepository;
_mapper = mapper;
}
这里，ReviewRepository需要被IReviewRepository取代。
因此，除了检查缺少的依赖项注入注册外，还值得检查现有的注册是否正确！