1. The model backing the 'MusicStoreDBContext' context has changed since the database was created.
Consider using Code First Migrations to update the database
Movie这个表是用来记录Model的版本号的，你每次重新生成一次数据库它就会重新给ModelHash列赋一个新值。
和原始数据库就会产生差异．
2. 自动将数据库的表名变复数，导致错误
方法一：使用TableAttribute为实体类指定映射的表名
[Table("User")]
public class User
{
[Key]
public int Id { get; set; }
public string Usn { get; set; }
public string Pwd { get; set; }
public DateTime Created { get; set; }
}
方法二：重写OnModelCreating方法不允许将表名变为复数形式
public class UserContext : DbContext
{
public UserContext()
: base("Name=SQLServer")
{ } protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<System.Data.Entity.ModelConfiguration.Conventions.PluralizingTableNameConvention>();
} public DbSet<User> User { get; set; }
}