@RyannnnnnR, how is the DB context registered? Is this an Entity Framework DB Context, and if so, is it registered in Startup correctly? I.e. do you have something like this somewhere:
public void ConfigureServices(IServiceCollection services)
{
// ... your other services
services.AddDbContext<UserDBContext >(options =>
options.UseSqlServer(Configuration.GetConnectionString("UserDBContext")));
}?
I think the way to show you what's going on is through 4 classes; Here is my Autofac Module for registering queries: https://github.com/RyannnnnnR/invoicer-backend-microservices/blob/master/src/Invoicer.Common/QueryBusModule.cs
Here is an example of a QueryHandler: https://github.com/RyannnnnnR/invoicer-backend-microservices/blob/master/src/UserService/Queries/Handlers/GetUserByIDQueryHandler.cs
And here is the repository referenced: https://github.com/RyannnnnnR/invoicer-backend-microservices/blob/master/src/UserService/Repositories/UserRepository.cs Which gets registered here: https://github.com/RyannnnnnR/invoicer-backend-microservices/blob/master/src/Invoicer.Common/RepositoryModule.cs
Hmmm...interesting. Can you provide the detail of the exception that get's raised?
Sure, thank you!
I have the following test case:
builder.RegisterType<Root1>().Keyed<IRootService>("A");
builder.RegisterType<Root2>().Keyed<IRootService>("B");
builder.RegisterType<Second>().AsSelf().SingleInstance();//.InstancePerLifetimeScope();//.InstancePerOwned<IRootService>();
IContainer container = builder.Build();
Owned<IRootService> rootService = container.ResolveKeyed<Owned<IRootService>>("B");
Second second = container.Resolve<Second>();
if(ReferenceEquals(rootService.Value.Second, second))
{
Debugger.Break();
}If Second is registered as SingleInstance, it works and the debugger breaks. If I use InstancePerLifetimeScope, it works and the debugger breaks not (entirely correct up until here). If I use InstancePerOwned, the following exception is thrown:
DependencyResolutionException: Unable to resolve the type 'AutofacTests.Program+Second' because the lifetime scope it belongs in can't be located. The following services are exposed by this registration:
AutofacTests.Program+Second
DependencyResolutionException: No scope with a tag matching 'AutofacTests.Program+IRootService' is visible from the scope in which the instance was requested.
If you see this during execution of a web application, it generally indicates that a component registered as per-HTTP request is being requested by a SingleInstance() component (or a similar scenario). Under the web integration always request dependencies from the dependency resolver or the request lifetime scope, never from the container itself.
@RyannnnnnR; from what I can tell at a glance, you're registering your IDbContext implementations as their interfaces:
builder.RegisterAssemblyTypes(ExecutingAssembly)
.Where(t => t.IsAssignableTo<IDbContext>())
.AsImplementedInterfaces();but you're resolving them from the type:
public UserRepository(UserDBContext dbContext)
{
_dbContext = dbContext;
}If you need to resolve as the type, you may want to change AsImplementedInterfaces() to AsSelf().
@alistairjevans; Thanks for the hint and it got me further! I ended up going with:
builder.RegisterAssemblyTypes(ExecutingAssembly)
.Where(t => t.IsClosedTypeOf(typeof(IDbContext<>)))
.AsSelf()
.InstancePerLifetimeScope();Except now whenever, I try and use the injected dbcontext, I get:
fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
An unhandled exception has occurred while executing the request.
System.Threading.Tasks.TaskCanceledException: A task was canceled.
at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnectionAsync(Boolean errorsExpected, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnectionAsync(Boolean errorsExpected, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenAsync(CancellationToken cancellationToken, Boolean errorsExpected)
at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.AsyncEnumerator.InitializeReaderAsync(DbContext _, Boolean result, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()
at Microsoft.EntityFrameworkCore.Query.ShapedQueryCompilingExpressionVisitor.SingleOrDefaultAsync[TSource](IAsyncEnumerable`1 asyncEnumerable, CancellationToken cancellationToken)
at Microsoft.EntityFrameworkCore.Query.ShapedQueryCompilingExpressionVisitor.SingleOrDefaultAsync[TSource](IAsyncEnumerable`1 asyncEnumerable, CancellationToken cancellationToken)
at UserService.Repositories.UserRepository.FindByIdAsync(String id) in /Users/ryan/Documents/invoicer-backend-microservices/src/UserService/Repositories/UserRepository.cs:line 31
at UserService.Queries.Handlers.GetUserByIDQueryHandler.Handle(GetUserByIDQuery query) in /Users/ryanr/Documents/invoicer-backend-microservices/src/UserService/Queries/Handlers/GetUserByIDQueryHandler.cs:line 19
at UserService.Controllers.UsersController.GetUserById(GetUserByIDQuery query) in /Users/ryanr/Documents/invoicer-backend-microservices/src/UserService/Controllers/UsersController.cs:line 43
at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfIActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask`1 actionResultValueTask)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.It looks like the same stacktrace is happening twice? Multiple threads? Is Autofac spawning them?
@RyannnnnnR you have a sample application available? Autofac is definitely not spawning any additional threads/tasks. Furthermore, the DbContext already provides generic access using context.Set<YourEntity>().
Also, you can simplify the registration like that I think:
builder.RegisterAssemblyTypes(ExecutingAssembly)
.AsClosedTypesOf((typeof(IDbContext<>))
.AsSelf()
.InstancePerLifetimeScope();I think what is happening is that more than one DbContext is created. The DbContext is not thread-safe. You can use InstancePerDependency() instead. Keep in mind that this has its downsides as well. I explained them here a bit:
https://stackoverflow.com/a/48783504/5397642
context.Set<Entity> would work in the context of my application; I need explicit DbContext classes to override onModelCreating and OnConfiguration
Secondly IDbContext<T> is a redundant layer of abstraction that you do not need. You don't need DbSet<T> at all. You can always use context.Set<T>() which is already generic. If you want to use the generic repository-pattern, that would make more sense.
Also, you are creating a new IContainer for each request in Send<TCommand>. You could always use Autofac with the extension Autofac.Extensions.DependencyInjection.
This has plenty of downsides because nothing you register with Autofac can be a singleton now for instance and also the performance suffers from building the container on each request. Instead, hook in the extension of Autofac and inject IServiceProvider if it's really necessary to create a scope.
InstancePerLifetimeScope is causing the problem, wouldn’t it stand to reason that InstancePerDependency, also wouldn’t work?
Do you kick off any background tasks during a request? If a background task is still using the lifetime scope of the request after the request has finished, this may happen.
Or, if you create a new lifetime scope (from the request scope) for a background unit-of-work pattern, and then let that continue after the request, this can happen.
Any ideas on why autofac it throwing the exception explain below in a .net core 3.1 web api application
https://stackoverflow.com/questions/61830753/autofac-throwing-exception-in-net-core-3-1-in-web-api-when-using-versioning-and
An exception was thrown while invoking the constructor 'Void .ctor(Microsoft.AspNetCore.Mvc.Infrastructure.IActionDescriptorCollectionProvider, Microsoft.AspNetCore.Mvc.Routing.ActionEndpointFactory)' on type 'ControllerActionEndpointDataSource'.
at Autofac.Core.Activators.Reflection.ConstructorParameterBinding.Instantiate() at Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext context, IEnumerable1 parameters)
at Autofac.Core.Resolving.InstanceLookup.CreateInstance(IEnumerable1 parameters)
An exception was thrown while activating Microsoft.AspNetCore.Mvc.Routing.ControllerActionEndpointDataSource.
Autofac is throwing an exception in a .net core 3.1 web api application. The exception is thrown at start up. The application is using versioning and Route Constraint which is causing the exception. Below is the controller and method that is causing the exception:
[ApiVersion("1.0")]
[Route("api/[controller]")]
[ApiController]
[Route("api/v{version:apiVersion}/[controller]")]
public partial class KDataServerController : KDataController
{
[HttpGet]
[RequireHttps]
[Route("{id:int:min(5):max(5)}/getconnetions/{info}", Name = "GetConnectionsRoute")]
[HttpGet]
public IActionResult GetConnections(long id, string info)
//public IActionResult Get()
{
var monkey = new { Id = 1, Name = "Forest Monkey", version = "1.0" };
return Ok(monkey);
}
}
The exception is thrown on the endpoints.MapControllers() line of code in the Startup class:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseHttpsRedirection();
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
}
Below is the stack trace showing the autofax exception:
at Autofac.Core.Activators.Reflection.ConstructorParameterBinding.Instantiate() at Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext context, IEnumerable1 parameters)
at Autofac.Core.Resolving.InstanceLookup.CreateInstance(IEnumerable1 parameters)
An exception was thrown while activating Microsoft.AspNetCore.Mvc.Routing.ControllerActionEndpointDataSource.
