Customer.cs

public class Customer
    {
        public string Name { get; set; }
        public string PhoneNumber { get; set; }
        public string Email { get; set; }

    }

DataContext.cs

public class DataContext : DbContext
    {
        public DataContext(DbContextOptions<DataContext> options)
            : base(options)
        {
        }

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

        public User GetUserData()
        {
            var query = (from a in Users
                         where a != null
                         select a).FirstOrDefault();
            
            return query;
        }

    }

IDataContext.cs

public interface IDataContext
    {
        User GetUserData();

    }

MainController.cs

public class MainController : Controller
{

private IDataContext _context;

public IActionResult MainPage()
        {
            var usernameQuery = _context.GetUserData();
            ViewData["DisplayUsername"] = usernameQuery;
            
            return View();
        }
    }
}

User.cs

public class User
    {
        public string Username { get; set; }
        public string Password { get; set; }

    }

web.config

  <connectionStrings>
    <add name="DataContext"
    providerName="System.Data.EntityClient"
    connectionString="Data Source=[SERVER-NAME];Initial Catalog=[TABLE-NAME];Integrated Security=True;MultipleActiveResultSets=True;user id=[USERNAME];password=[PASSWORD];"/>
  </connectionStrings>