CODEWITHSUNDEEP
asp.net-coredependency-injectionrazor-pagesdbcontext
albinioni
albinioni

Reputation: 115

Passing DI object to constructor of new class

So, in Razor Pages I know how I can use Dependency Injection to inject my DbContext (for example) in the constructor to access it in the whole class by creating a global private readonly variable.

However, let's say I have a DbManager class that makes all the calls to the DB (to avoid making them from every Razor Page in the application), then I have to pass the context to that class, even though I'm using (at least to my knowledge) dependency injection there as well.

Shouldn't it be able to find it without actually passing it to the constructor, and isn't that the whole point of dependency injection, or am I missing something?

What is the best practice here? Just feels wrong to pass the context as a parameter! I suspect I'm doing something wrong... Am I?

    public class IndexModel : PageModel
    {
        private readonly AppDbContext _context;
    
        public IndexModel(AppDbContext context)
        {
            _context = context;
        }
    
        public void OnGet()
        {
            var result = new DbManager(_context).GetStuffFromDb(); // Feels weird to pass the context as a parameter here!
        }
    }

Upvotes: 1

Views: 1216

Answers (1)

Nkosi
Nkosi

Reputation: 247088

If you are not making any explicit reference calls to the context within IndexModel then only inject the DbManager.

private readonly IDbManager manager;
    
public IndexModel(IDbManager manager) {
    this.manager = manager;
}
    
public void OnGet() {
    manager.GetStuffFromDb();
    
    //...
}

The context will be injected into the manager when being resolved, provided it (the context) was also registered in the composition root

//...

builder.Services.AddScoped<IDbManager, DbManager>();
builder.Services.AddDbContext<AppDbContext>(....);

//...

Reference Explicit Dependencies Principle

Upvotes: 3

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