MVC Link连接数据库增删改查方法的不同写法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace MvcApplication5注册验证.Models
{
    public class ZhuceBF
    {
        private mydboDataContext _Context = new mydboDataContext();
        public List<zhuce> Select()
        {
            return _Context.zhuce.ToList();
        }
        public zhuce Selectbyid(string id)
        {
            var query = _Context.zhuce.Where(p=>p.ID==id);
            if (query.Count()>0)
            {
                return query.First();
            }
            return null;
        }
        public void Insert(string id,string username,string userpwd)
        {
            if (username == "" || username == " ")
            {
            }
            else
            {
                zhuce data = new zhuce();
                data.ID = id;
                data.Username = username;
                data.Userpwd = userpwd;
                _Context.zhuce.InsertOnSubmit(data);
                _Context.SubmitChanges();
            }
        }

        public void Update(string id, string username, string userpwd)
        {
            var query = _Context.zhuce.Where(p=>p.ID==id);
            if (query.Count()>0)
            {
                zhuce data = query.First();
                data.ID = id;
                data.Username = username;
                data.Userpwd = userpwd;
            }
            _Context.SubmitChanges();
        }

        public void Delete(string id)
        {
            var query = _Context.zhuce.Where(p=>p.ID==id);
            if (query.Count()>0)
            {
                zhuce data = query.First();
                _Context.zhuce.DeleteOnSubmit(data);
                _Context.SubmitChanges();
            }
        }
        //简写方法
        public void Insert( zhuce data)
        {
            _Context.zhuce.InsertOnSubmit(data);
            _Context.SubmitChanges();
        }
        public void Updata(zhuce data)
        {
           // zhuce sdata = _Context.zhuce.Where(p=>p.ID==data.ID).First();
            //上面这一局查询一堆选择第一条
            //下面这一局是查询一条，结果一样
           zhuce sdata = _Context.zhuce.Single(p=>p.ID ==data.ID);

           sdata.ID = data.ID;
           sdata.Username = data.Username;
           sdata.Userpwd = data.Userpwd;
        }
        //删除多条数据
        public void Delete(string name)
        {
            List<zhuce> list= _Context.zhuce.Where(p => p.Username == name).ToList();

                _Context.zhuce.DeleteAllOnSubmit(list);
                _Context.SubmitChanges();
        }
        //模糊查询
        public List<zhuce> SelectByname(string name)
        {
            return _Context.zhuce.Where(r=>r.Username.Contains(name)).ToList();
        }

        //表达式查询
        public List<zhuce> Selectbyname(string name)
        {
            //query相当于一条数据，_Context,zhuce相当于List<zhuce>
            var a=from query1 in _Context.zhuce where query1.Username.Contains(name) select query1;
            return a.ToList();
        }
    }
}