LINQ.Contains超过2100记录报异常Exception的问题

LINQ.Contains超过2100记录报异常Exception的问题  

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LINQ的异常: 传入的表格格式数据流(TDS)远程过程调用(RPC)协议流不正确。此 RPC 请求中提供了过多的参数。最多应为 2100。

代码：标红的地方会报错误

 var pid = (from p in PSLVList

                       select p.ProductID).Distinct().ToList();

            var AllSortListTemp = (from p in pdc.Product_Standard

                                   join j in pdc.Product_Journey on p.Product_Id equals j.Product_Id

                                   where pid.Contains(p.Product_Id)

                                   orderby p.Duration ascending

                                   select new AllSortListTempView

                                   {

                                      Begin_City_Id = p.Begin_City_Id,

                                      

                                      End_City_Id =  p.End_City_Id,

                                      Product_Id = p.Product_Id,

                                      Duration = p.Duration,

                                      Pre_Booking_Day = p.Pre_Booking_Day,

                                      Arrive_City_ID = j.Arrive_City_ID,

                                      Day_No = j.Day_No,

                                      Product_Sub_Type = p.Product_Sub_Type

                                   }

                                ).Distinct().ToList();

报错的地方就是.Contains函数，当AnotherList的元素个数超过2100，LINQ的.Contains最大支持2100，超过就会报这个异常。

解决办法很简单，只要将调用数据源的AsEnumerable()运算符就可以了。例如：

var AllSortListTemp = (from p in pdc.Product_Standard.AsEnumerable()

                                   join j in pdc.Product_Journey on p.Product_Id equals j.Product_Id

                                   where pid.Contains(p.Product_Id)

                                   orderby p.Duration ascending

                                   select new AllSortListTempView

                                   {

                                      Begin_City_Id = p.Begin_City_Id,

                                      

                                      End_City_Id =  p.End_City_Id,

                                      Product_Id = p.Product_Id,

                                      Duration = p.Duration,

                                      Pre_Booking_Day = p.Pre_Booking_Day,

                                      Arrive_City_ID = j.Arrive_City_ID,

                                      Day_No = j.Day_No,

                                      Product_Sub_Type = p.Product_Sub_Type

                                   }

                                ).Distinct().ToList();

为什么.AsEnumerable()这么神奇？

从MSDN看到，调用这个方法会返回一个 IEnumerable<T> 对象，而大家知道，和IQueryable比较起来，IEnumerable<T>是用了LINQ2Object的方式，而不是LINQ2SQL的方式，前者数据是在内存中处理的，而后者是在server上运 行的。换句话说，本地数据源用IEnumerable<T>，数据在内存中，并且查询的逻辑可以直接用你所定义的方法的逻辑（因为有上下
文）；远程数据源用IQueryable<T>，无法直接使用你所定义的方法的逻辑，必须先生成表达式树，查询由源对象处 理；IQueryable<T>类型可以在最终的执行前加一些方法，然后再返回最终的IQueryable<T>；而 IEnumerable<T>已经包含了你执行查询后的所有结果，这时你的添加方法都是在已经有的结果集里进行。一言以蔽之，上面的2100的问题解决方法就是避免了LINQ2SQL生成表达式树查询远程服务器!

这个方法有个副作用：调用dataContext.GetTable<MyEntity>().AsEnumerable()的副作用是吃内存，如果这个table很大，估计内存空间会消耗很大。