C#•16mo ago

❔ Question about setting up dependency injection (console app with no async stuff)

So I've been trying to set up a dependency injection in my program for the first time to no avail. From what I've learned, a dependency injection allows you to use methods from another class without having to explicitly instantiate a new instance of the class which allows for loosely coupled code and less dependencies. I was told I should be injecting my DBContext instead of calling a new context every time I do a database action. I think the way I have been approaching this fix is wrong in that I'm creating an interface for my Helpers class when in reality I should be making an interface for my PhoneBookContext class. Am I on the right track? Any feedback is appreciated. Pasted code: https://paste.mod.gg/hhwsmajvkxnq/2

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41 Replies

phaseshift•16mo ago

I was told I should be injecting my DBContext instead of calling a new context every time I do a database action

that is true for ASP.net because it's the framework that resolves stuff from the container. If you're in a console app, you're going to have to resolve at least the root item manually yourself.

I should be making an interface for my PhoneBookContext class

No. doing helpers = new() and then new-ing up a PhoneBookContext in helpers is the opposite of dependency injection.

a dependency injection allows you to use methods from another class without having to explicitly instantiate a new instance of the class which allows for loosely coupled code and less dependencies.

That doesn't sound correct. loose coupling comes from class design and proper use of interfaces or other de-coupling mechanisms.

GIGA BRAINOP•16mo ago

i think i see, it creates more dependencies?

phaseshift•16mo ago

It's the same dependency. It's not injected. It's tightly coupled But its the only db context you;re going to have. It's ok to be relatively tightly coupled there But it's better to inject as it is reduced coupling

GIGA BRAINOP•16mo ago

so instead of getting loosely coupled code from dependency injections, its reducing coupling instead

phaseshift•16mo ago

? I dont know what youre referring to

GIGA BRAINOP•16mo ago

this and how my definition of DI is wrong

phaseshift•16mo ago

di is using constructors

GIGA BRAINOP•16mo ago

constructor injection thats the kind of injection i'm trying to do here, right?

phaseshift•16mo ago

It's what would be better. I don't see any attempt at it in your code

GIGA BRAINOP•16mo ago

yeah im confused on how to set it up in the first place looking at the microsoft documentation, i'm assuming i need an interface

phaseshift•16mo ago

if doing it manually, the only place 'new' should be is in Main No, interfaces not needed

GIGA BRAINOP•16mo ago

oh could you explain what you mean by Main? people have said that before and i dont know if they mean like program.cs or something i remember there used to be a public static void main thing for csharp

phaseshift•16mo ago

yes

GIGA BRAINOP•16mo ago

is that what youre talking about? but doesn't every class have that

phaseshift•16mo ago

the entry point of the program

GIGA BRAINOP•16mo ago

oh nvm on my last statement

phaseshift•16mo ago

No.There is exactly one main in an app (zero in pure libs)

GIGA BRAINOP•16mo ago

And to make sure, this is in my program.cs right? or unless i define it in a different class

phaseshift•16mo ago

what is in program.cs?

GIGA BRAINOP•16mo ago

and don't use program.cs for my main

using PhoneBookApp;
using PhoneBookApp.Data;
using PhoneBookApp.Models;
using Microsoft.Extensions.DependencyInjection;

Menu menu = new Menu();
menu.ShowMenu();

using PhoneBookApp;
using PhoneBookApp.Data;
using PhoneBookApp.Models;
using Microsoft.Extensions.DependencyInjection;

Menu menu = new Menu();
menu.ShowMenu();

literally just this

phaseshift•16mo ago

oh for top level statements.

GIGA BRAINOP•16mo ago

i have dependencies everywhere uhh yeah?

phaseshift•16mo ago

Menu menu = new Menu();
menu.ShowMenu();

Menu menu = new Menu();
menu.ShowMenu();

Yes, that is your main

GIGA BRAINOP•16mo ago

got it, so all my "new" stuff should be in main and then i inject from there? is this what you mean by the root?

phaseshift•16mo ago

yes. So here your root is Menu if you were using a container, you'd have something small like var menu = container.GetService<Menu>() and it would make everything else that needs to be injected into Menu's ctor but manually you might need to do

var d1 = new ...
var d2 = new ...
...
var d_n = new ...
var menu = new Menu(d1, d2, ..., d_n);

var d1 = new ...
var d2 = new ...
...
var d_n = new ...
var menu = new Menu(d1, d2, ..., d_n);

GIGA BRAINOP•16mo ago

oh i see well i dont mind listing them all out in my main it would only be like 3 or 4 but youre saying I dont need an interface, so after would I follow the documentation as normal? i'm following this and it says after i need to register my service

GIGA BRAINOP•16mo ago

https://learn.microsoft.com/en-us/dotnet/core/extensions/dependency-injection

Dependency injection - .NET

Learn how to use dependency injection within your .NET apps. Discover how to registration services, define service lifetimes, and express dependencies in C#.

GIGA BRAINOP•16mo ago

but then im not using an interface with a concrete type so i'm confused on that should i just learn how to do DI when I learn about asp.net core?

phaseshift•16mo ago

without an interface it's just services.AddSingleton<Menu>() as opposed to services.AddSingleton<IMenu, Menu>()

GIGA BRAINOP•16mo ago

so something like this?

using PhoneBookApp;
using PhoneBookApp.Data;
using PhoneBookApp.Models;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

Menu menu = new();
Helpers helpers = new();
UserInput input = new();
Validate validate = new();
using PhoneBookContext _context = new();

HostApplicationBuilder builder = Host.CreateApplicationBuilder();

builder.Services.AddSingleton<Program>();

using IHost host = builder.Build();
host.Run();

menu.ShowMenu();

using PhoneBookApp;
using PhoneBookApp.Data;
using PhoneBookApp.Models;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

Menu menu = new();
Helpers helpers = new();
UserInput input = new();
Validate validate = new();
using PhoneBookContext _context = new();

HostApplicationBuilder builder = Host.CreateApplicationBuilder();

builder.Services.AddSingleton<Program>();

using IHost host = builder.Build();
host.Run();

menu.ShowMenu();

phaseshift•16mo ago

no, none of that is related validate not used. input not used. helpers not used. _context not used AddSingleton<Program> looks pointless

GIGA BRAINOP•16mo ago

i think im just gonna have to come back to this later i have no idea what im doing

Philémon•16mo ago

i used something like this when i tried Console Dependency Injection. I dont know if its the perfect way to do DI in consoles, but i think its not that bad. You could use this example:

using IceCreamVendor.Core.Data;
using IceCreamVendor.Core.Logic;
using IceCreamVendor.Core.Service;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

IConfigurationBuilder builder = new ConfigurationBuilder()
    .SetBasePath(Directory.GetCurrentDirectory())
    .AddJsonFile("appsettings.json", optional: false);

IConfiguration config = builder.Build();

using IHost host = Host.CreateDefaultBuilder(args)
    .ConfigureServices((_, services) => services
        .AddTransient<IIceCreamService, IceCreamService>()
        .AddTransient<ILogService, LogService>()
        .AddTransient<ISellService, SellService>()
        .AddDbContext<IceCreamContext>(options => options.UseSqlServer(config.GetConnectionString("DefaultConnection")))
        .AddTransient<IceCreamBusiness>()
        )
    .Build();

RunBusiness(host.Services);

await host.RunAsync();

static void RunBusiness(IServiceProvider services)
{
    using IServiceScope serviceScope = services.CreateScope();
    IServiceProvider provider = serviceScope.ServiceProvider;

    IceCreamBusiness business = provider.GetService<IceCreamBusiness>();
    business?.RunBusiness();
}
}

using IceCreamVendor.Core.Data;
using IceCreamVendor.Core.Logic;
using IceCreamVendor.Core.Service;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

IConfigurationBuilder builder = new ConfigurationBuilder()
    .SetBasePath(Directory.GetCurrentDirectory())
    .AddJsonFile("appsettings.json", optional: false);

IConfiguration config = builder.Build();

using IHost host = Host.CreateDefaultBuilder(args)
    .ConfigureServices((_, services) => services
        .AddTransient<IIceCreamService, IceCreamService>()
        .AddTransient<ILogService, LogService>()
        .AddTransient<ISellService, SellService>()
        .AddDbContext<IceCreamContext>(options => options.UseSqlServer(config.GetConnectionString("DefaultConnection")))
        .AddTransient<IceCreamBusiness>()
        )
    .Build();

RunBusiness(host.Services);

await host.RunAsync();

static void RunBusiness(IServiceProvider services)
{
    using IServiceScope serviceScope = services.CreateScope();
    IServiceProvider provider = serviceScope.ServiceProvider;

    IceCreamBusiness business = provider.GetService<IceCreamBusiness>();
    business?.RunBusiness();
}
}

Philémon•16mo ago

I see that my repo is public, you can see it all at this address: https://github.com/PhilemonPhilippin/IceCreamVendor-repo/tree/master But i am junior dev and i made it at my even earlier stage, so take it with a grain of salt if i may say

GitHub

GitHub - PhilemonPhilippin/IceCreamVendor-repo: App to practice log...

App to practice loggings and DI. Contribute to PhilemonPhilippin/IceCreamVendor-repo development by creating an account on GitHub.

Philémon•16mo ago

The best thing to do in this case imo : watch a tutorial (youtube or else) on the subject, try it on your own, research more deeply for every bit you don't understand, and when you write code, F12 keyboard shortcut on every Microsoft base library that you don't understand will be your friend! You got this 💪

GIGA BRAINOP•16mo ago

thanks for the input! Im gonna try and understand your code tomorrow and see how it goes 💯 and definitely for sure will try again with DI

Becquerel•16mo ago

using PhoneBookApp;
using PhoneBookApp.Data;
using PhoneBookApp.Models;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

// Create the host and the container.
HostApplicationBuilder builder = Host.CreateApplicationBuilder();

// Tell the container what classes you want to use in DI.
builder.Services.AddSingleton<Menu>();
builder.Services.AddSingleton<Helpers>();
builder.Services.AddSingleton<UserInput>();
builder.Services.AddSingleton<Validate>();
builder.Services.AddTransient<PhoneBookContext>();

// Tell the container to figure out the web of dependencies for your classes.
// If your web of dependencies doesn't make sense it will throw an exception.
var host = builder.Build();

// Tell the container to give you an instance of a class you registered in DI.
var menu = host.Services.GetRequiredService<Menu>();

// Use the class to do stuff.
// The instance will have everything it asks for in its constructor automatically
// given to it by the DI container.
menu.ShowMenu();

using PhoneBookApp;
using PhoneBookApp.Data;
using PhoneBookApp.Models;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

// Create the host and the container.
HostApplicationBuilder builder = Host.CreateApplicationBuilder();

// Tell the container what classes you want to use in DI.
builder.Services.AddSingleton<Menu>();
builder.Services.AddSingleton<Helpers>();
builder.Services.AddSingleton<UserInput>();
builder.Services.AddSingleton<Validate>();
builder.Services.AddTransient<PhoneBookContext>();

// Tell the container to figure out the web of dependencies for your classes.
// If your web of dependencies doesn't make sense it will throw an exception.
var host = builder.Build();

// Tell the container to give you an instance of a class you registered in DI.
var menu = host.Services.GetRequiredService<Menu>();

// Use the class to do stuff.
// The instance will have everything it asks for in its constructor automatically
// given to it by the DI container.
menu.ShowMenu();

Using the host is different than using DI. Hosting in .NET lets you get other stuff, namely graceful shutdowns, built-in logging, etc., etc. But if you just want to learn DI then you can wire just that up like this.

GIGA BRAINOP•16mo ago

wow thank you it was such a headache trying to understand how to set it up literally multiple days of no progress will try and understand this tomorrow 💯

Becquerel•16mo ago

no prob. DI is confusing until it 'clicks' and then it becomes very simple feel free to message me if you want further explanations

GIGA BRAINOP•16mo ago

sounds good, will do thank you again

Accord•16mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Question about setting up dependency injection (console app with no async stuff)