public class UserInfo
    {
        [Key]
        public string openid { get; set; }
        public string session_key { get; set; }
        public string nickName { get; set; }
        public string avatarUrl { get; set; }
        public int gender { get; set; }
        public string province { get; set; }
        public string city { get; set; }
        public string country { get; set; }

    }

    public class DemoContex : DbContext
    {
        /// <summary>
        /// 使用“codefirst”连接字符串。根据实际情况修改连接字符串
        /// </summary>
        public DemoContex()
                : base("data source=127.0.0.1;initial catalog=Demo;user id=sa;password=1234")
        {
        }

        /// <summary>
        /// code first默认生成的表名会加上s,这段代码生成的数据表名不带s
        /// </summary>
        /// <param name="modelBuilder"></param>
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
        }

        /// <summary>
        /// 实体类型添加到 DbSet
        /// </summary>
        public virtual DbSet<UserInfo> UserInfo { get; set; }
    }