MVC学习之路（1） EF 增删查改合集

首先再Model中创建一个类[WMBlogDB]

public class WMBlogDB : DbContext
    {
       
        //连接字符串。
        public WMBlogDB()
            : base("name=WMBlogDB")
        {
        }

//sysUserInfo.cs 是一个model里面有id name等等信息
        public DbSet<sysUserInfo> sysUserInfos { get; set; }

       protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
           //移除表明为复数
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
            // //自动添加实现EntityTypeConfiguration的类
            modelBuilder.Configurations.AddFromAssembly(Assembly.GetExecutingAssembly());
            base.OnModelCreating(modelBuilder);
       }
        //为您要在模型中包含的每种实体类型都添加 DbSet。有关配置和使用 Code First  模型
        //的详细信息，请参阅 http://go.microsoft.com/fwlink/?LinkId=390109。

        
    }

1】新增，网上有觉得十分良好的两种方式，先举例。

方式一 
 WMBlogDB db = new WMBlogDB();
sysUserInfo sos = new sysUserInfo()
            {
                Name = "Admin111",
                PWD = "123456",
                RealName = "超级管理员", 
            };
            //创建ef容器对象，并后去当前实体对象的状态管理对象
            DbEntityEntry<sysUserInfo> entry = db.Entry<sysUserInfo>(sos);
            //添加
            entry.State = EntityState.Added;
//保存到数据库
db.SaveChanges()
方式二
   using (WMBlogDB dbs = new WMBlogDB()) {
                sysUserInfo sys = new sysUserInfo();
                Stopwatch st = new Stopwatch();
                st.Start();
                db.sysUserInfos.Add(new sysUserInfo
                {
                     Name = "Admin111",
                PWD = "123456",
                RealName = "超级管理员", 
                });
               dbs.SaveChanges()
            }
//其实这里可以不用using包裹，可以和方式一一样先new WMBlogDB，然后直接使用。
//这里使用using：只要离开了这个代码段就自动调用这个类实例的Dispose。
//要达到这样的目的，用try...catch来捕捉异常也是可以的，但用using也很方便

2】删除

 #region 删除
            //方式一 
            using (WMBlogDB db = new WMBlogDB())
            {
                sysUserInfo us = new sysUserInfo()
                {

                    uID = 68
                };
                db.Entry<sysUserInfo>(us).State = EntityState.Deleted;
                return Content(db.SaveChanges().ToString() + "ss");
            }

            //方式二
            using (WMBlogDB dbs = new WMBlogDB())
            {
                List<sysUserInfo> list = dbs.sysUserInfos.Where(u => u.uLoginName == "Admin111" & u.uLoginPWD == "123456").ToList();
                //Any表示只要集合中有值就返回true 否者返回float
                if (list != null && list.Any())
                {
                    foreach (sysUserInfo item in list)
                    {
                        dbs.sysUserInfos.Remove(item);
                    }
                    // dbs.SaveChanges();
                }
                //  int ss = dbs.SaveChanges();
                return Content(dbs.SaveChanges().ToString());
            }
//在执行代码期间，发现方式1只能通过id来删除，通过其他值则会报错。这点有人解决的话，感谢留言
            #endregion

3】修改

    #region 修改
            //方法1
            using (WMBlogDB dbs = new WMBlogDB())
            {
                var model = dbs.sysUserInfos.FirstOrDefault(u => u.uLoginName == "Admin111");
                model.uLoginName = "TS";
                model.uLoginPWD = "123";
                return Content(dbs.SaveChanges().ToString());
                //这种方式一次只能修改一条数据
            }
            //方法二
            using (WMBlogDB dbs = new WMBlogDB())
            {
                sysUserInfo model = new sysUserInfo()
                {
                    uID =78,
                    uRealName = "xiugai"
                };
                //根据 uid寻找数据，然后uRealName是修改之后数据，
                //有点类似添加

                //获取代理对象类为Detaceh
                //需要先引用 System.Data.Entity.Infrastructure
                DbEntityEntry entry = dbs.Entry(model);
                //1、将代理类的状态修改成 Unchanged 
                //2、将代理类中的需要更新的字段的IsModified修改成true
                entry.State = EntityState.Unchanged;
                entry.Property("uRealName").IsModified = true;
                //解决对一个或多个实体验证失败 的方法：关闭EF的实体合法性检查
                dbs.Configuration.ValidateOnSaveEnabled = false;
                return Content(dbs.SaveChanges().ToString() );
                //这种方式目前也只能一次修改一条数据
            }
            #endregion

4】查询，

 ArrayList list = new ArrayList(); 
            
             using (WMBlogDB dbs = new WMBlogDB()){

                 var ss = (from us in dbs.sysUserInfos orderby us.uID descending select us).ToList<sysUserInfo>();
                 string cw = "";
//通过foreach获取值，
                 foreach (sysUserInfo sof in ss)
                 {
                     cw += sof.uLoginName + "|||";
                     list.Add(sof.uLoginName);
                 }
                 string name = list[1].ToString();
                 return Content(name);

5】：分页

using (thEntities db = new thEntities())
            {
                if (zx == 0)
                {
                    var ss = (from us in db.Users orderby us.ID descending select us).ToList<Users>();
                    uu = ss;
                }
                else
                {
                    var ss = ((from us in db.Users orderby us.ID descending select us).Skip(num * (page - 1)).Take(num)).ToList<Users>();
                    uu = ss;
                }

            } 

 6】：join查询

方式一

 using (thEntities1 db = new thEntities1()) {
                var sql = db.Users.Join(db.Study, u => u.LID, g => g.LIDs, (u, g) => new { name = u.Name, naem2 = g.Name, name3 = u.Password });
                var list = sql.ToList();
                return View();
            }



                var sql = db.表1.Join(db.表2, u => u.表1匹配列名, g => g.表2匹配列名, (u, g) => new { name = u.表一列名, naem2 = g.表二列名, name3 = u.表一列名 });

方式二
using (thEntities1 db = new thEntities1()) {

                var query = from d in db.Users
                            join b in db.Study
//注意，相连接的字段用equals连接
                            on d.LID equals b.LIDs
                            select new {
                            name1=b.Name,
                            name2=b.LIDs,
                            name3=b.Name
                            };
                var list = query.ToList();
                return View();
            }

7】：ef使用sql语句

 
方法一
using (thEntities1 db = new thEntities1()) {
                string SQLStr = string.Format("UPDATE Study SET Name=@name where IDs=@id ");
                SqlParameter[] p = new SqlParameter[]{
                new SqlParameter("@id",5),
                new SqlParameter("@name","EGHTT")
                };
                db.Database.ExecuteSqlCommand(SQLStr, p);
            }
方法二[方法1简化版本]
 using (thEntities1 db = new thEntities1())
            {
                string value = "22";
                string id = "22";
                db.Database.ExecuteSqlCommand("UPDATE dbo.Storage SET  Name ='" + value + "' WHERE  ID='" + id + "'");
            }

7.1】EF提高查询的方法AsNoTracking

 using (thEntities1 db = new thEntities1()) {
                db.Users.AsNoTracking().Where(u => u.LID == 22).ToList();
            }

7.2】

  List<CodeV> SJO = db.Database.SqlQuery<CodeV>("SELECT * FROM [dbo].[CodeV] WHERE Name='" + txm + "'").ToList<CodeV>();

8】使用存储过程

首先是存储过程（事物）
ALTER PROC [dbo].[AddItems]
@txm VARCHAR(500),
@num INT,
@jsr VARCHAR(200),
@people INT,
@Msg VARCHAR(100) OUTPUT
AS
BEGIN

BEGIN TRAN
BEGIN TRY
---SQL操作语句     
    COMMIT
 END TRY
 BEGIN CATCH
     SET @Msg='失败！'
     ROLLBACK
 END CATCH
 
END


然后是执行存储过程
  List<SqlParameter> paramArry = new List<SqlParameter>();
            paramArry.Add(new SqlParameter("@txm", txm));
            paramArry.Add(new SqlParameter("@num", num));
            paramArry.Add(new SqlParameter("@jsr", jsr));
            paramArry.Add(new SqlParameter("@people", people));
            SqlParameter param = new SqlParameter("@Msg", SqlDbType.VarChar, 100);
            param.Direction = ParameterDirection.Output;
            paramArry.Add(param);
            using (WHEntity db = new WHEntity())
            {
                try
                {
                    db.Database.ExecuteSqlCommand("EXEC [AddItems] @txm,@num,@jsr,@people,@Msg OUT", paramArry.ToArray());
                    Msg = paramArry[4].Value.ToString();
                }
                catch (Exception ex)
                { 
                    string gg = ex.ToString(); 
                    string sss = ex.Message;

                   Msg=sss +"22222"+ gg; 
                }

            }

9】Other

聚合函数 Average、Count、Max、Min、Sum
using(thEntities1 db=new  thEntities1()){
var li=db.User.Max(p=>p.Num);
}

10】补充

控制器中返回json格式  

 JsonConvert.SerializeObject(new { code = 0, msg = "", count = numss, data = dr });

// JsonConvert.SerializeObject(new { 参数1= 值1, 参数2= 值2});

之后遇到新的知识将会在此补充