Conditional dependency resolver on run-time (.net Core)

Question

I have two classes PaymentGatewayFoo, PaymentGatewayBoo that both implements a common interface of IPaymentGateway:

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Answer 1

This is how I approach this type of problem where I have cases that needs different implementations.

public abstract class PaymentGateway : IPaymentGateway 
{
    public long Identifier {get;}
    ...
}

public class PaymentGatewayFoo : PaymentGateway
{
    public long Identifier => 1;
    ...
}

public class PaymentGatewayBoo : PaymentGateway
{
    public long Identifier => 2;
    ...
}

public class PaymentGatewayProvider
{
    private IPaymentGateway[] gateways;
    public PaymentGatewayProvider(IPaymentGateway[] gateways)
    {
         this.gateways = gateways;
    }

    public IPaymentGateway GetGateForClient(bool f) //This can be anything that you can use to identify which payment gateway you need
    {
         //As an example I would usually pass in a client or something that I can then use to identify which payment provider is mapped to a certain client, this way you can have hundreds of payment providers, but in your case you just had a boolean, so I used that
         if(f)
              return gateways.First(f=> f.Identifier == 1);
         return gateways.First(f=> f.Identifier != 1);
    }
}


public class OrderService
{
    private readonly PaymentGatewayProvider _provider;

    public void DoOrder(bool isFoo)
    {
        var service = _provider.GetGateForClient(isFoo);
        this._service.Pay();
    }
}

The way you identify payment providers can be anything, I just used longs as an example here, but you can map it to an enum and rather use that to do identification, then you pass the enum to the GetGateForClient method to get the correct payment gateway

This might not compile out of the box, but should give you a general idea of how to solve the problem.