Creating a database class in MVC

Question

I want to expand on the question below:

How to instantiate a DbContext in EF Core

I've done the above in my controller, but am now trying to create DataAccess.cs where I want all my database methods/queries to happen. For example, I have the following so far:

Controller:

public class HomeController : Controller
    {
        DataAccess da = new DataAccess() { };

        private readonly DatabaseContext db;

        public HomeController(DatabaseContext reg)
        {
            db = reg;
        } 

    [HttpPost, ValidateAntiForgeryToken]
    public IActionResult Register(User model)
    {       
        model.WindowsAuth = User.Identity.Name;

        if (ModelState.IsValid) 
        {
            da.Registration(model, db);                
            return RedirectToAction("Index");
        }

In DataAccess.cs

 public class DataAccess
 {        
    public void Registration(User model, DatabaseContext db)
    {
        User newUser = new User();
        db.Users.Add(model);
        db.SaveChanges();
    }
 }

Database context

public class DatabaseContext :DbContext
{


    public DatabaseContext(DbContextOptions<DatabaseContext> options)
               : base(options)
    {
    }

    public DbSet<User> Users { get; set; }

}

The above works, but I want to add more methods into DataAccess.cs. Will I need to pass my database as a parameter from the controller everytime? The db variable comes out as null when I try to instantiate the context class in my data access class. I am new to MVC, so any further reading or sources related to this would be appreciated.

Answer 1

With the help of DI you should inject DataAccess to controller and DatabaseContext to DataAccess. Also don't forget to register DataAccess at DI container:

public class HomeController : Controller
{
    private readonly DataAccess da;// = new DataAccess() { };
    //private readonly DatabaseContext db;   
    public HomeController(DataAccess da)
    {
        this.da = da;
    } 
}

public class DataAccess
{
    private readonly DatabaseContext db;     
    public DataAccess(DatabaseContext db)
    {
        this.db = db;
    }

    public void Registration(User model/*, DatabaseContext db*/)
    {
        User newUser = new User();
        db.Users.Add(model);
        db.SaveChanges();
    }
}