EF基础一

EF基础，从0开始：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Data.Entity;using System.ComponentModel.DataAnnotations;namespace CodeFirstNewDatabase{    class Program    {        static void Main(string[] args)        {            using (var db = new BloggingContext())            {                Console.Write("Enter a name for a new Blog: ");                var name = Console.ReadLine();                var blog = new Blog { Name = name };                db.Blogs.Add(blog);                db.SaveChanges();                var query = from b in db.Blogs                            orderby b.Name                            select b;                Console.WriteLine("All blogs in the database:");                foreach (var item in query)                {                    Console.WriteLine(item.Name);                }                Console.WriteLine("Press any key to exit...");                Console.ReadKey();            }        }    }    public class Blog    {        public int BlogID { get; set; }        public string Name { get; set; }        public string Url { get; set; }        public virtual IList<Post> Posts { get; set; }    }    public class Post    {        public int PostID { get; set; }        public string Title { get; set; }        public string Content { get; set; }        public int BlogId { get; set; }        public virtual Blog Blog { get; set; }    }    public class User    {        [Key]         // annotation: keyattribute        public string Username { get; set; }        public string Displayname { get; set; }    }    public class BloggingContext : DbContext    {                 public DbSet<Blog> Blogs { get; set; }        public DbSet<Post> Posts { get; set; }        public DbSet<User> Users { get; set; }        protected override void OnModelCreating(DbModelBuilder modelBuilder)           // fluent api: override onmodelcreating method        {            modelBuilder.Entity<User>()                .Property(u => u.Displayname)                .HasColumnName("Display_name");        }           }}