ASP.NET MVC issue resolving DbContext to a Derived class

Question

I do have a ASP.NET Core 2.0 application with Microsoft.Extensions.DependencyInjection.

I added my Context ApplicationDbContext to the Startup.cs file:

services.AddDbContext<ApplicationDbContext>(options => 
    options.UseSqlServer(DefaultConnection));

My ApplicationDbContext inherits the DbContext class:

In a generic controller I require a DbContext class:

public GenericController(DbContext context){

However Microsoft.Extensions.DependencyInjection cannot resolve the DbContext to the ApplicationDbContext registered service.

How can I inject the required DbContext class into my service class?

I'm able to change the GenericController, but the project where GenericController lies does not have reference to the ApplicationDbContext.

I'm developing a middleware, it should require DbContext that should be specialized in other projects. So the controller is in the middleware, it does not have a reference to the specialized class.

NightOwl888 · Accepted Answer · 2018-03-08 15:11:16Z

2

the project where GenericController lies does not have reference to the ApplicationDbContext

This is 100% of your issue.

You either need to ensure that ApplicationDbContext is in a project that the services that use it can reference:

public GenericController(ApplicationDbContext context){

or you need to create an IApplicationDbContext that is implemented by ApplicationDbContext that can be referenced from the services that use it:

public GenericController(IApplicationDbContext context){

Injecting DbContext alone isn't going to cut it because it doesn't expose any of the tables that your application needs to use.

answered Mar 8, 2018 at 15:11

NightOwl888

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2 Comments

Daniel Santos Over a year ago

unfortunately I'm developing a middleware, it should require a specific DbContext that should be specialized in other projects. So the controller is in the middleware, it does not have a reference to the specialized class. only to the parent one. I think that i could resolve child classes.

NightOwl888 Over a year ago

If it doesn't have a reference to the concrete ApplicationDbContext then you will need to make a IApplicationDbContext interface in an assembly that is shared between the middleware assembly and the assembly that defines ApplicationDbContext.

Daniel Santos · Accepted Answer · 2018-04-17 22:10:22Z

1

I solved it by Just adding a Transient from derived class to parent class below the AddContext command

services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(DefaultConnection));
services.AddTransient<DIADbContext,ApplicationDbContext>();

answered Apr 17, 2018 at 22:10

Daniel Santos

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Comments

Vasile Pojoga · Accepted Answer · 2020-09-01 11:08:26Z

1

Another solution can be to register the DbContext with a custom factory which will return the already registered ApplicationDbContext instance from the container:

services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(DefaultConnection));
services.AddScoped<DbContext, ApplicationDbContext>(s => s.GetService<ApplicationDbContext>());

answered Sep 1, 2020 at 11:08

Vasile Pojoga

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