c#中Linq to Sql 增删除的实例

抽像类：  

 public abstract class abuserall
    {
        public abstract iqueryable<user_all> finduserall();
        public abstract user_all finduserallbyid(int userid);
        public abstract void add(user_all user);
        public abstract void update(user_all user);
        public abstract void delete(user_all user);
        public abstract void save();
    }

using system;
using system.collections.generic;
using system.linq;
using system.web;

namespace wf.models.dal
{
    public class userdal:idal.abuserall
    {
        private pl_modeldatacontext db = new pl_modeldatacontext();
        public override iqueryable<user_all> finduserall()
        {
            return db.user_all;
        }

        public override void delete(user_all user)
        {
            db.user_all.deleteonsubmit(user);
        }

        public override void save()
        {
            db.submitchanges();
        }

        public override user_all finduserallbyid(int userid)
        {
            return db.user_all.singleordefault(o => o.int == userid);
        }

        public override void add(user_all user)
        {
            db.user_all.insertonsubmit(user);
        }

        public override void update(user_all user)
        {
            var editstudent = db.user_all.singleordefault<user_all>(s => s.int == user.int);
            if (editstudent != null)
            {
                editstudent.username = user.username;
                editstudent.address = user.address;
            }
            db.submitchanges();

        }
    }
}

using system;
using system.collections.generic;
using system.linq;
using system.web;
using system.web.mvc;

namespace wf.controllers
{
    public class usercontroller : controller
    {
        models.dal.userdal dbuser = new models.dal.userdal();
        //
        // get: /user/

        public actionresult userlist()
        {

            return view(dbuser.finduserall());
        }

 
        //
        // get: /user/create

        public actionresult create()
        {
            return view();
        }

        //
        // post: /user/create

        [httppost]
        public actionresult create(formcollection collection,models.user_all user)
        {
            try
            {
                dbuser.add(user);
                dbuser.save();
                return redirecttoaction("userlist");
            }
            catch
            {
                return view();
            }
        }

        //
        // get: /user/edit/5

        public actionresult useredit(int id)
        {

            return view(dbuser.finduserallbyid(id));
        }

        //
        // post: /user/edit/5

        [httppost]
        public actionresult useredit(models.user_all user, formcollection collection)
        {
            try
            { 
                dbuser.update(user);
                dbuser.save();
                return redirecttoaction("userlist");
            }
            catch
            {
                return view();
            }
        }
    }
}