EF 保证线程内唯一 上下文的创建

1、ef添加完这个对象，就会自动返回这个对象数据库的内容，比如下面这个表是自增ID

最后打印出来的ID  就是自增的结果

2、lambda 中怎么select *

var userInfoList = from u in db.UserInfo
                   where u.ID == 345
                  select u;

 3、返回类型 IQueryable<T>

它继承 IEnumerable<T> 相当于集合

延迟加载机制  用到的时候才去数据库查

4、两种删除标记

db.UserInfo.Remove(userInfo);
db.Entry<UserInfo>(userInfo).State = System.Data.EntityState.Deleted;

 5、删除的时候可以不用先查数据库

UserInfo userInfo = new UserInfo() {ID=344};
//db.UserInfo.Remove(userInfo);//这样不能用remove 只能用State,Remove必须先查出来
db.Entry<UserInfo>(userInfo).State = System.Data.EntityState.Deleted;
db.SaveChanges();

 6、modelfirst 生成ddl   了解dml ddl dcl区别

 在生成的时候（vs2012 sqlserver2008很可能会出错）http://www.bubuko.com/infodetail-1266884.html

7、导航属性

订单属于哪个人  外键会自动添加这个人的ID

savechange 设计模式：工作单元模式 ：一个业务对多张表的操作，只连一次数据库，完成条记录的更新

            Model2Container db = new Model2Container();
            //人
            Customer customer = new Customer() {CustomerName="zhangsan",CustomerPwd="123", SubTime=DateTime.Now };
            //订单
            OrderInfo orderInfo1 = new OrderInfo() { ID = Guid.NewGuid(), OrderNum = "10001", CreateDateTime = DateTime.Now,Customer=customer };
            OrderInfo orderInfo2 = new OrderInfo() { ID = Guid.NewGuid(), OrderNum = "10002", CreateDateTime = DateTime.Now, Customer = customer };
            db.Customer.Add(customer);
            db.OrderInfo.Add(orderInfo1);
            db.OrderInfo.Add(orderInfo2);
            db.SaveChanges();//默认的已经开启了事务。 工作单元模式。（UnitOfwork）

 Orderinfor 是Customer的导航属性

            Model2Container db = new Model2Container();
            var customerList = from c in db.Customer
                               select c;
            foreach (var customer in customerList)
            {
                Response.Write(customer.CustomerName+":");


                foreach (var orderInfo in customer.OrderInfo)//延迟加载。
                {
                    Response.Write(orderInfo.OrderNum);
                }
            }

不过  导航属性效率比较低，检测sqlserver发现是 查询两次

下面的写法好些

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

namespace WebApplication1
{
    public partial class WebForm2 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }
        //创建一个人 添加俩订单
        protected void Button1_Click(object sender, EventArgs e)
        {
            Model2Container db = new Model2Container();
            //人
            Customer customer = new Customer() {CustomerName="zhangsan",CustomerPwd="123", SubTime=DateTime.Now };
            //订单
            OrderInfo orderInfo1 = new OrderInfo() { ID = Guid.NewGuid(), OrderNum = "10001", CreateDateTime = DateTime.Now,Customer=customer };
            OrderInfo orderInfo2 = new OrderInfo() { ID = Guid.NewGuid(), OrderNum = "10002", CreateDateTime = DateTime.Now, Customer = customer };
            db.Customer.Add(customer);
            db.OrderInfo.Add(orderInfo1);
            db.OrderInfo.Add(orderInfo2);
            db.SaveChanges();//默认的已经开启了事务。 工作单元模式。（UnitOfwork）
        }
        //打印出所有人的订单号
        protected void Button2_Click(object sender, EventArgs e)
        {
            Model2Container db = new Model2Container();
            var customerList = from c in db.Customer
                               select c;
            foreach (var customer in customerList)
            {
                Response.Write(customer.CustomerName+":");


                foreach (var orderInfo in customer.OrderInfo)//延迟加载。
                {
                    Response.Write(orderInfo.OrderNum);
                }
            }
        }
        //打印出这个人的订单号
        protected void Button3_Click(object sender, EventArgs e)
        {
            Model2Container db = new Model2Container();
            //var customerInfoList = from c in db.Customer
            //                   where c.ID == 1
            //                   select c;
            //var customerInfo = customerInfoList.FirstOrDefault();
            //foreach (var orderInfo in customerInfo.OrderInfo)
            //{
            //    Response.Write(orderInfo.OrderNum);
            //}

            var orderInfoList = from o in db.OrderInfo
                               where o.CustomerID == 1
                               select o;
            foreach (var orderInfo in orderInfoList)
            {
                Response.Write(orderInfo.OrderNum);
            }
                           
        }
        
        //打印出这个订单的客户名称
        protected void Button4_Click(object sender, EventArgs e)
        {
             Model2Container db = new Model2Container();
             var orderInfoList = from o in db.OrderInfo
                                 where o.OrderNum == "10001"
                                 select o;
             var orderInfo = orderInfoList.FirstOrDefault();
             Customer customer = orderInfo.Customer;
             Response.Write(customer.CustomerName);
        }

        //删除某个客户下的  所有的订单
        protected void Button5_Click(object sender, EventArgs e)
        {
            Model2Container db = new Model2Container();
            //var customer = (from c in db.Customer
            //                where c.ID == 1
            //                select c).FirstOrDefault();
            //var orderInfoList = customer.OrderInfo;
            //while (orderInfoList.Count > 0)
            //{
            //    var orderInfo = orderInfoList.FirstOrDefault();
            //    db.Entry<OrderInfo>(orderInfo).State = System.Data.EntityState.Deleted;
            //}
            //db.SaveChanges();

            var orderList = from o in db.OrderInfo
                            where o.CustomerID == 2
                            select o;

        }

    }
}

简单查询：var result = from c in Entities.Customer select c;
条件查询：
普通linq写法： var result = from c in Entities.Customer where c.Gender ==‘w’ select c;
Lambda表达式写法： var result = from c in Entities.Customer.Where<Customer>(c =>c.Gender==‘w’);
排序分页写法： 

IQueryable<Customers> cust10 = (from c in customers
                                         orderby c.CustomerID
                                         select c).Skip(0).Take(10);

左外连接：可以的连接有Join 和 GroupJoin 方法。GroupJoin组联接等效于左外部联接，它返回第一个（左侧）数据源的每个元素（即使其他数据源中没有关联元素）。

 var query = from d in edm.Order_Details
                   join order in edm.Orders
                   on d.OrderID equals order.OrderID
                   select new
                    {
                        OrderId = order.OrderID,
                        ProductId = d.ProductID,
                        UnitPrice = d.UnitPrice
                     };

 8、操作方式

dbfirst 连接数据库  映射对象（edmx）

modelfirt 创建空数据模型（edmx） 添加模型 右键根据模型生成数据库

9、codefirt 根据连接字符串 自动创建数据库

vs 2012  可以直接添加一个空的模型自动添加引用 其他的版本 不可以

 学生表

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CodeFirstDemo
{
   public class StudentInfo
    {
       [Key] //主键
       public int Id { get; set; }
       [StringLength(32)] //指定长度
       [Required] //不可为空
       public string StuName { get; set; }
        [Required] //不可为空
       public DateTime SubTime { get; set; }
       //关系  一个班级可以有多个学生
       public virtual ClassInfo ClassInfo { get; set; }
    }
}

 

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CodeFirstDemo
{
   public class ClassInfo
    {
       [Key]
       public int Id { get; set; }
       [StringLength(32)]
       [Required]
       public string ClassName { get; set; }
       [Required]
       public DateTime CreateTime { get; set; }
       //导航属性  一个班级有多个学生
       public virtual ICollection<StudentInfo> StudentInfo { get; set; }
    }
}

数据库上线文 daset  表示对这个类有curd权限

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CodeFirstDemo
{
   public class CodeFirstDbContext:DbContext
    {
        //connStr 连接字符串
       public CodeFirstDbContext()
           : base("name=connStr")
       {

       }
       protected override void OnModelCreating(DbModelBuilder modelBuilder)
       {
           //不加这句话，自动创建的表后边都有s  如 classinfo->classsinfos  
           modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
       }
    
       public DbSet<ClassInfo> ClassInfo { get; set; }
       public DbSet<StudentInfo> StudentInfo { get; set; }
    }
}

主程序 有则不创建数据库 没有则创建

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CodeFirstDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            CodeFirstDbContext db = new CodeFirstDbContext();
            db.Database.CreateIfNotExists();//没有数据库自动创建，有则不
            ClassInfo classInfo = new ClassInfo();
            classInfo.ClassName = "0413班";
            classInfo.CreateTime = DateTime.Now;
            db.ClassInfo.Add(classInfo);
            db.SaveChanges();

        }
    }
}

 保证线程内唯一

为了保证有两个EF上下文  F1  F2都改了集合  而F1先savechange，F2再保存就会发生冲突

解决方案：单列模式  只new一次  

以上解决方案错误，所有人拿到一个实例，所有人都往上下文类添加数据，越来越大，内存会爆，服务器会瘫，还不能释放，一个人释放了，其他人就废了

所以

解决方案：线程内唯一

httpContext 是通过 callContext保证线程内唯一的
其实写httpContext也是可以的

using CZBK.HeiMaOA.Model;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Runtime.Remoting.Messaging;
using System.Text;
using System.Threading.Tasks;

namespace CZBK.HeiMaOA.DAL
{
   public class DBContextFactory
    {
       /// <summary>
       /// 保证在一次请求过程中只创建一次EF上下文实例.
       /// </summary>
       /// <returns></returns>
       public static DbContext CreateDbContext()
       {
           DbContext dbContext = (DbContext)CallContext.GetData("dbContext");
           if (dbContext == null)
           {
               dbContext = new OAEntities();
               CallContext.SetData("dbContext", dbContext);
           }
           return dbContext;
       }
    }
}

using CZBK.HeiMaOA.Model;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CZBK.HeiMaOA.DAL
{
  public  class BaseDal<T>where T:class,new()
    {
       // OAEntities Db = new OAEntities();
      DbContext Db = DBContextFactory.CreateDbContext();//完成EF上下文创建.
        /// <summary>
        /// 基本查询方法
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <returns></returns>
        public IQueryable<T> LoadEntities(System.Linq.Expressions.Expression<Func<T, bool>> whereLambda)
        {
            return Db.Set<T>().Where<T>(whereLambda);
        }
        /// <summary>
        /// 分页方法
        /// </summary>
        /// <typeparam name="s">排序的约束</typeparam>
        /// <param name="pageIndex">当前页码</param>
        /// <param name="pageSize">每页显示记录数</param>
        /// <param name="totalCount">总条数</param>
        /// <param name="whereLambda">过滤条件</param>
        /// <param name="orderbyLambda">排序条件</param>
        /// <param name="isAsc">排序方式</param>
        /// <returns></returns>
        public IQueryable<T> LoadPageEntities<s>(int pageIndex, int pageSize, out int totalCount, System.Linq.Expressions.Expression<Func<T, bool>> whereLambda, System.Linq.Expressions.Expression<Func<T, s>> orderbyLambda, bool isAsc)
        {
            var temp = Db.Set<T>().Where<T>(whereLambda);
            totalCount = temp.Count();
            if (isAsc)//如果成立表示升序
            {
                temp = temp.OrderBy<T, s>(orderbyLambda).Skip<T>((pageIndex - 1) * pageSize).Take<T>(pageSize);
            }
            else
            {
                temp = temp.OrderByDescending<T, s>(orderbyLambda).Skip<T>((pageIndex - 1) * pageSize).Take<T>(pageSize);
            }
            return temp;

        }
        /// <summary>
        /// 删除数据
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public bool DeleteEntity(T entity)
        {
            Db.Entry<T>(entity).State = System.Data.EntityState.Deleted;
         //   return Db.SaveChanges() > 0;
            return true;
        }
        /// <summary>
        /// 更新
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public bool UpdateEntity(T entity)
        {
            Db.Entry<T>(entity).State = System.Data.EntityState.Modified;
           // return Db.SaveChanges() > 0;
            return true;
        }
        /// <summary>
        /// 添加数据
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public T AddEntity(T entity)
        {
            Db.Set <T>().Add(entity);
            //Db.SaveChanges();
            return entity;
        }
    }
}

//httpContext是线程内唯一
//这样保证EF上下文线程内唯一
EFFristModelEntities db = null;
if (HttpContext.Current.Items["db"] == null)
{
    db = new EFFristModelEntities();
    HttpContext.Current.Items["db"] = db;
}
else
{
    db = HttpContext.Current.Items["db"] as EFFristModelEntities;
}

EF  执行SQL

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

namespace CZBK.ItcastOA.BLL
{
   public partial class KeyWordsRankService:BaseService<Model.KeyWordsRank>,IBLL.IKeyWordsRankService
    {
       /// <summary>
       /// 将统计的明细表的数据插入。
       /// </summary>
       /// <returns></returns>
        public bool InsertKeyWordsRank()
        {
            string sql = "insert into KeyWordsRank(Id,KeyWords,SearchCount) select newid(),KeyWords,count(*)  
from SearchDetails where DateDiff(day,SearchDetails.SearchDateTime,getdate())<=7 
group by SearchDetails.KeyWords";
            return this.CurrentDBSession.ExecuteSql(sql)>0;
        }
       /// <summary>
       /// 删除汇总中的数据。
       /// </summary>
       /// <returns></returns>
        public bool DeleteAllKeyWordsRank()
        {
            //用这句删除表中的数据是非常快的
            string sql = "truncate table KeyWordsRank";
           return this.CurrentDBSession.ExecuteSql(sql)>0;
        }
        public List<string> GetSearchMsg(string term)
        {
           //KeyWords like term%
            string sql = "select KeyWords from KeyWordsRank where KeyWords like @term";
           return this.CurrentDBSession.ExecuteQuery<string>(sql, new SqlParameter("@term",term+"%" ));
        }
    }
}

EF 返回datatable

/// <summary>
       /// EF SQL 语句返回 dataTable
       /// </summary>
       /// <param name="db"></param>
       /// <param name="sql"></param>
       /// <param name="parameters"></param>
       /// <returns></returns>
       public static DataTable SqlQueryForDataTatable(this Database db,
                string sql,
                SqlParameter[] parameters)
       {

           SqlConnection conn = new System.Data.SqlClient.SqlConnection();
           conn.ConnectionString = db.Connection.ConnectionString;
           if (conn.State != ConnectionState.Open)
           {
               conn.Open();
           }
           SqlCommand cmd = new SqlCommand();
           cmd.Connection = conn;
           cmd.CommandText = sql;

           if (parameters.Length>0)
           {
               foreach (var item in parameters)
               {
                   cmd.Parameters.Add(item);
               }
           }

          
           SqlDataAdapter adapter = new SqlDataAdapter(cmd);
           DataTable table = new DataTable();
           adapter.Fill(table);
           return table;
       }

调用如下

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            GridView1.DataSource = GetDataTable();
            GridView1.DataBind();
        }
    }


    public DataTable GetDataTable()
    {
        GardenHotelContext context = new GardenHotelContext();
        int LanType = 0;
        int state = 0;
        SqlParameter[] sqlparams=new SqlParameter[2];
        sqlparams[0]=new SqlParameter("LanType",LanType);
        sqlparams[1]=new SqlParameter("state",state);
        DataTable DataTable = context.Database.SqlQueryForDataTatable("select LeaveName,LeaveEmail from LeaveInfo where LanType=@LanType and State=@State", sqlparams);
        return DataTable;
     
    }

另一种方法

public DataTable GetDataTable2()
    {
        GardenHotelContext context = new GardenHotelContext();

        var list = (from l in context.LeaveInfoes
                   group l by l.LanType into g
                   select new
                   {
                       g.Key,
                       num = g.Count()
                   }).ToList();

        return PubClass.ListToDataTable(list);

    }

#region  反射List To DataTable


        /// <summary>  
        /// 将集合类转换成DataTable  
        /// </summary>  
        /// <param name="list">集合</param>  
        /// <returns></returns>  
        public static DataTable ListToDataTable(IList list)
        {
            DataTable result = new DataTable();
            if (list.Count > 0)
            {
                PropertyInfo[] propertys = list[0].GetType().GetProperties();
                foreach (PropertyInfo pi in propertys)
                {
                    result.Columns.Add(pi.Name, pi.PropertyType);
                }

                for (int i = 0; i < list.Count; i++)
                {
                    ArrayList tempList = new ArrayList();
                    foreach (PropertyInfo pi in propertys)
                    {
                        object obj = pi.GetValue(list[i], null);
                        tempList.Add(obj);
                    }
                    object[] array = tempList.ToArray();
                    result.LoadDataRow(array, true);
                }
            }
            return result;
        }  

        #endregion

http://www.cnblogs.com/wlflovenet/archive/2011/12/30/EF11.html

linq 包括方法语法（lambda格式） 查询语法
帮助文档推荐尽可能使用查询语法也就是正经linq格式
from n in list
where n.StartWith("s")
orderby n //查询方法排序 按照N排序
select n;
找到集合中以S开头的
方法语法排序
var result=list.OrderBy(n=>n).where(...)
倒序：orderByDescending()