Injection of configuration when creating an instance from a JSON file

Question

I have a code snippet that creates an instance based on the configuration specified in the JSON file (I am thinking about LoginLogic)

public ILoginModule GetLoginModule()
{
    if (loginModule == null)
    {
        loginModule = new LoginModule.LoginModule(_configuration);

        Type loginLogicType = CreateTypeFromConfiguration("LoginModule", "LoginLogic", "MyProject.Modules.LoginModule.Logic.LoginLogic");
        loginModule.SetLoginLogic((ILoginLogic)Activator.CreateInstance(loginLogicType));
    }
    return loginModule;
}

Here's what the LoginLogic class looks like

public class LoginLogic : ILoginLogic
{
    private IConfiguration _configuration;
    protected ILoginRepository loginRepository;

    public LoginLogic()
    {
    }

    public LoginLogic(IConfiguration configuration)
    {
        _configuration = configuration;
        loginRepository = new LoginRepository(_configuration);
    }
}

Activator uses an empty constructor to create an object

I need to have the data that I call in the next constructor

loginRepository I can move because it does not change anything

What to do with configuration? It is injected automatically by Net. Core

We obviously can't see a lot of your custom code here, but it looks like you're just reinventing the wheel of Configure<TOptions>. Why not use what's already built in? — Chris Pratt
– Chris Pratt, Commented Jul 19, 2019 at 18:25

Nkosi · Accepted Answer · 2019-07-19 15:20:16Z

5

There is a little known static class in NetCore which allows you to the CreateInstance but with injection..

From the top of my head, I think its in the Microsoft.Extensions.DependencyInjection.Abstractions namespace and its called ActivatorUtilities.

You call it like so:

var instance = ActivatorUtilities.CreateInstance(ServiceProvider, typeof(typeToInstantiate));

It requires a IServiceProvider instance which contains all the objects it can inject for.

Is that what you're looking for?

edited Jul 19, 2019 at 15:20

Nkosi

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answered Jul 19, 2019 at 15:12

Robert Perry

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