APIDAL层方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;
using Model;
using System.Data.SqlClient;

namespace DAL
{
    public class Fdal
    {
        /// <summary>
        /// 下拉
        /// </summary>
        /// <returns></returns>
      public List<Sclass>SelectClass()
        {
            string sql = "select * from Sclass";
            var dt = DBHelper.GetDataTable(sql);
            var strlist = JsonConvert.SerializeObject(dt);
            var list = JsonConvert.DeserializeObject<List<Sclass>>(strlist);
            return list;
        }
        /// <summary>
        /// 显示
        /// </summary>
        /// <returns></returns>
        public List<Student>ShowStuden()
        {
            string sql = "select * from Sclass c join Student s on c.Cid=s.Cid";
            var dt = DBHelper.GetDataTable(sql);
            var strlist = JsonConvert.SerializeObject(dt);
            var list = JsonConvert.DeserializeObject<List<Student>>(strlist);
            return list;
        }
        /// <summary>
        /// 根据班级查询
        /// </summary>
        /// <param name="cid"></param>
        /// <returns></returns>
        public List<Student>SelectStuden(int cid)
        {
            string sql = @"select * from Sclass c join Student s on c.Cid=s.Cid where c.Cid="+cid;
            var dt = DBHelper.GetDataTable(sql);
            var strlist = JsonConvert.SerializeObject(dt);
            var list = JsonConvert.DeserializeObject<List<Student>>(strlist);
            return list;
        }
        /// <summary>
        /// 删除学生
        /// </summary>
        /// <param name="sid"></param>
        /// <returns></returns>
        public int DeleStudent(int sid)
        {
            SqlParameter[] pa = new SqlParameter[] { 
                new SqlParameter("@sid",sid),
            };
            return DBHelper.ExecuteNonQueryProc("p_delete",pa);
        }
        /// <summary>
        /// 删除班级
        /// </summary>
        /// <param name="sid"></param>
        /// <returns></returns>
        public int DeleClass(int cid)
        {
            SqlParameter[] pa = new SqlParameter[] {
                new SqlParameter("@cid",cid),
            };
            return DBHelper.ExecuteNonQueryProc("p_delecla", pa);
        }
        /// <summary>
        /// 添加学生
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public int AddStudent(Student s)
        {
            SqlParameter[] pa = new SqlParameter[] {
                new SqlParameter("@name",s.Sname),
                new SqlParameter("@age",s.Age),
                new SqlParameter("@cid",s.Cid)
            };
            return DBHelper.ExecuteNonQueryProc("p_adds", pa);
        }
        /// <summary>
        /// 添加班级
        /// </summary>
        /// <param name="c"></param>
        /// <returns></returns>
        public int AddClass(Sclass c)
        {
            SqlParameter[] pa = new SqlParameter[]
                {
                    new SqlParameter("@cname",c.Cname),
                };
            return DBHelper.ExecuteNonQueryProc("p_addclass", pa);
        }

         
    }
}