ASP.NET Core database configuration with dependency injection issue

Question

I ran in to a problem 6 days ago and i still can't figure it out.

I'm setting up a DBContext using DI:

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddDbContext<ApplicationContext>(options =>
        options.UseSqlite(Configuration.GetConnectionString("DefaultConnection")));

    services.AddMvc();

    // Add application services.
    services.AddTransient<IEmailSender, AuthMessageSender>();
    services.AddTransient<ISmsSender, AuthMessageSender>();
}

The database file path is configurered in the appsettings.json

{
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=xxxx.db"
  },
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  }
}

And I'm creating a DBContext like this (https://learn.microsoft.com/en-us/ef/core/miscellaneous/configuring-dbcontext)

public class ApplicationContext : DbContext
{
        public DbSet<Network> xxxx { get; set; }
        public DbSet<NetworkEntry> xxxx { get; set; }
        public ApplicationContext(DbContextOptions<ApplicationContext> options)
        : base(options)
        { }
}

My controller code:

public JsonResult Index(ApplicationContext db)
{
    return Json(db.Networks);
}

It compiles and runs. If I use the other way of configuring the DB, it works 100% problem free:

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder.UseSqlite("Filename=./blog.db");
}

The problem I'm having:

System.InvalidOperationException: Could not create a model binder for model object of type 'xxx.Data.ApplicationContext'.
   at Microsoft.AspNetCore.Mvc.ModelBinding.ModelBinderFactory.CreateBinder(ModelBinderFactoryContext context)
   at Microsoft.AspNetCore.Mvc.Internal.DefaultControllerArgumentBinder.<BindModelAsync>d__8.MoveNext()
--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.DefaultControllerArgumentBinder.<BindArgumentsCoreAsync>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeNextResourceFilter>d__22.MoveNext()
--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeAsync>d__20.MoveNext()
--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Builder.RouterMiddleware.<Invoke>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.MigrationsEndPointMiddleware.<Invoke>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.<Invoke>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.<Invoke>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.<Invoke>d__7.MoveNext()

Any clues?

Answer 1

I have just solved a similar problem. The problem for me was that I'd misunderstood the dependency injection. The context doesn't get passed to the Controller method, but to the Controller's constructor.

public class NetworksController : Controller
{
    private readonly ChoirAdminContext db;

    public NetworksController(ApplicationContext context)
    {
        db = context;
    }

    public JsonResult Index()
    {
        return Json(db.Networks);
    }
}