InvalidOperationException：尝试激活控制器时无法解析类型“*Models.LandingPageContext”的服务

Question

我有一个名为“LandingPage”的数据库，并使用此命令在我的 asp.net mvc 核心中映射了数据库表：-

 Scaffold-DbContext "Server=(localdb)\ProjectsV13;Database=LandingPage;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models

然后我添加了一个控制器并选择了其中一个模型，但是当我尝试访问控制器时，我在网络浏览器中遇到了这个异常：-

An unhandled exception occurred while processing the request.
InvalidOperationException: Unable to resolve service for type 'LandingPage.Models.LandingPageContext' while attempting to activate 'LandingPage.Controllers.QuestionsController'.
Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, bool isDefaultParameterRequired)
Stack Query Cookies Headers Routing 
InvalidOperationException: Unable to resolve service for type 'LandingPage.Models.LandingPageContext' while attempting to activate 'LandingPage.Controllers.QuestionsController'.
Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, bool isDefaultParameterRequired)
lambda_method(Closure , IServiceProvider , object[] )
Microsoft.AspNetCore.Mvc.Controllers.ControllerActivatorProvider+<>c__DisplayClass4_0.<CreateActivator>b__0(ControllerContext controllerContext)
Microsoft.AspNetCore.Mvc.Controllers.ControllerFactoryProvider+<>c__DisplayClass5_0.<CreateControllerFactory>g__CreateController|0(ControllerContext controllerContext)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Answer 1

需要在 Startup.cs 中将 DbContext 注册为服务，以便在其构造函数中将其注入到控制器中：

Startup.cs：

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

QuestionsController.cs：

public class QuestionsController: Controller
{
    public QuestionsController(LandingPageContext dbContext)
    {
    }
}

Dependency injection in ASP.NET Core 中的更多信息。