ASP .Net Core Web APIs Dependency Injection Class with Multiple Constructors

Question

I am using Asp .net core 2.2 with built-in DI. I want to inject service that has multiple constructors that fulfill the container conditions. And I can't remove the other constructor for backward compatibility. Example code:

public interface IService{
   void DoSomthing();
}

public class Implementation : IService
{
    public Implementation(IService1 service1)
    {

    }

    public Implementation(IService1 service1, IService2 service2)
    {

    }

    public void DoSomthing()
    {
        // Do something
    }
}

I registered all these services in the DI container example:

services.AddScoped<IService, Implementation>();

Now I have another class that uses IService as DI:

public class ClassA : IService
{
    public ClassA(IService service)
    {

    }
}

How Dependency injection container will intialize this class using which constructor?:

public Implementation(IService1 service1)
Or
public Implementation(IService1 service1, IService2 service2)

and what is the rule for choosing between them?

score 1 · Accepted Answer · answered Jan 07 '20 at 16:02

1

If you only bind IService1 it will call the constructor that only takes IService1. If you also bind IService2, it will call the constructor with IService2. If you have a class (like your ClassA) that only has one constructor that only takes an IService1, it will call that constructor regardless of whether you've bound an IService2.

answered Jan 07 '20 at 16:02

rory.ap

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I need to bind both. – Husam Zidan Jan 07 '20 at 16:05
Then it will call the constructor that takes both. – rory.ap Jan 07 '20 at 16:07
So the rule is to call the constructor with a high number of fulfilled parameters?. thanks. – Husam Zidan Jan 07 '20 at 16:14

ASP .Net Core Web APIs Dependency Injection Class with Multiple Constructors

1 Answers1