How to Register Multiple Services, Multiple implementation in separate class and call it in ConfigureServices method?

Question

Traditionally, we register multiple services, multiple interfaces under ConfigureServices method in the Startup class. This is feasible if we have five or ten registrations. But what if we have fifty or more such registrations?

public void ConfigureServices(IServiceCollection services) {
  service.AddTransient<ISQLDB, SQLDB>();
  service.AddTransient<IEmployeeBusiness, EmployeeBusiness>();
  service.AddTransient<IEmployeeRepository, EmployeeRepository>();
  service.AddTransient<IEmployeeValidation, EmployeeValidation>();
  service.AddTransient<IDepartmentBusiness, DepartmentBusiness>();
  service.AddTransient<IDepartmentRepository, EmployeeRepository>();
  service.AddTransient<IDepartmentValidation, EmployeeValidation>();
  ...
  ...
  ...
  // some 50 or more
}

I want to move the registering part to another custom InjectDependency class and call this in ConfigureServices method like:

public class InjectDependency{
    public InjectDependency(IServiceCollection service)
    {
      service.AddTransient<ISQLDB, SQLDB>();
      service.AddTransient<IEmployeeBusiness, EmployeeBusiness>();
      service.AddTransient<IEmployeeRepository, EmployeeRepository>();
      service.AddTransient<IEmployeeValidation, EmployeeValidation>();
      service.AddTransient<IDepartmentBusiness, DepartmentBusiness>();
      service.AddTransient<IDepartmentRepository, EmployeeRepository>();
      service.AddTransient<IDepartmentValidation, EmployeeValidation>();
      ...
      ...
      ...
      ...
    }
  }

Is there any way to achieve this?

What isn't working with your code? Since you're passing your IServiceCollection reference to your InjectDependency class, this should work just fine. Are you receiving an error? Are you just not sure how to call this? Note that since this is a stateless function, it may make more sense to treat it as a static method rather than a constructor. — Jeremy Caney
– Jeremy Caney, Commented Nov 13, 2020 at 20:49

Jeremy Caney · Accepted Answer · 2021-07-25 02:42:14Z

2

Your code should work fine as is, though there are a couple of improvements you could make.

First, your InjectDependency() constructor is essentially stateless, so it would make more sense as a static method rather than a constructor. Second, to take that one step further, you could set it up as an extension method off of the IServiceCollection interface, which is a really common approach to this scenario:

public class ServiceCollectionExtensions {
  public static IServiceCollection AddBusinessLogic(this IServiceCollection services) {
    services.AddTransient<ISQLDB, SQLDB>();
    services.AddTransient<IEmployeeBusiness, EmployeeBusiness>();
    services.AddTransient<IEmployeeRepository, EmployeeRepository>();
    …    
    return services;
  }
}

Then, in your Startup class, you'd simply call this like:

public void ConfigureServices(IServiceCollection services) {
  services.AddBusinessLogic();
}

If you have that many implementations, however, you might also try to determine if there's a common pattern or convention you can use to dynamically register them. For example, in your sample data, a lot of your implementations share the same base identifier as the interface. If that pattern holds, it might be easier to write code that automates that. There's a good example of this on the question Built-in dependency injection with conventions.

edited Jul 25, 2021 at 2:42

answered Nov 13, 2020 at 21:07

Jeremy Caney

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2 Comments

Vu Re Vu Over a year ago

Thanks using extension method it worked. Here is full implementation

Vu Re Vu Over a year ago

I don't see any option to mark your response as Answer. How do I mark the response as Answer?

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