C# EF创建及更新数据库 Database.SetInitializer用法

EF Code First Model字段改变数据库的字段也跟着自动改变
public class Context:DbContext
{
    public Context():base("UserDB")
    {
        //自动创建表，如果Entity有改到就更新到表结构
        Database.SetInitializer<Context>(new MigrateDatabaseToLatestVersion<Context, ReportingDbMigrationsConfiguration>());
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        //modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();//这句是不要将EF生成的sql表名不要被复数 就是表名后面不要多加个S
    }

    internal sealed class ReportingDbMigrationsConfiguration : DbMigrationsConfiguration<Context>
    {
        public ReportingDbMigrationsConfiguration()
        {
            AutomaticMigrationsEnabled = true;//任何Model Class的修改將会直接更新DB
            AutomaticMigrationDataLossAllowed = true;
        }
    }

    public DbSet<UserInfo> UserInfo { get; set; }

//数据库不存在时重新创建数据库
Database.SetInitializer(new CreateDatabaseIfNotExists<DbContext>());
//每次启动应用程序时创建数据库
Database.SetInitializer(new DropCreateDatabaseAlways<DbContext>());
//模型更改时重新创建数据库
Database.SetInitializer(new DropCreateDatabaseIfModelChanges<DbContext>());
//从不创建数据库
Database.SetInitializer<DbContext>(null);