QuickCHAT/Source/Model.cs

using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;

namespace QuickCHAT.Models {
    public class DatabaseContext : DbContext {
        public DbSet<User> Users { get; set; }

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

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) {

        }

        protected override void OnModelCreating(ModelBuilder modelBuilder) {
            modelBuilder.Entity<User>()
                .HasAlternateKey(u => u.Username)
                .HasName("AK_Username");
        }
    }

    public class User {
        public int UserID { get; set; }
        public string Username { get; set; }
        public string Password { get; set; }
        public string First { get; set; }
        public string Last { get; set; }
        public string Description { get; set; }
    }
}