Linq to entity 笔记

1.返回指定字段生成实体

            List<Product> q = db.Product.Where(a => a.ProductName == "a  ")
                    .Select(a => new { ProductName = a.ProductName, AddTime = a.AddTime }).ToList() // ToList() 将数据读取到内存中  然后转化成SQL
                    .Select(a => new Product() { ProductName = a.ProductName, AddTime = a.AddTime }).ToList();
                // 生成语句
                /*               SELECT 
               1 AS [C1], 
               [Extent1].[ProductName] AS [ProductName], 
               [Extent1].[AddTime] AS [AddTime]
               FROM [dbo].[Product] AS [Extent1]
               WHERE N'a' = [Extent1].[ProductName]  */

                foreach (Product p in q)
                {
                    Console.WriteLine(p.ProductName);
                }

2. 插入 ：效率不行  方法有待 拓展 ，提高

                Product pro = new Product();
                pro.ProductName = "I  lOVER YOU";
                pro.ProductPrice = 12m;
                pro.AddTime = DateTime.Now;
                db.AddToProduct(pro);

                pro = new Product();
                pro.ProductName = "I  lOVER YOU";
                pro.ProductPrice = 12m;
                pro.AddTime = DateTime.Now;
                db.AddToProduct(pro);

                db.SaveChanges();
                /*  生成语句
                 exec sp_executesql N'insert [dbo].[Product]([ProductName], [ProductPrice], [ProductDisc], [AddTime])
values (@0, @1, null, @2)
select [ProductID]
from [dbo].[Product]
where @@ROWCOUNT > 0 and [ProductID] = scope_identity()',N'@0 nvarchar(12),@1 decimal(18,0),@2 datetime',@0=N'I  lOVER YOU',@1=12,@2='2012-03-15 23:05:21.860'
go
exec sp_executesql N'insert [dbo].[Product]([ProductName], [ProductPrice], [ProductDisc], [AddTime])
values (@0, @1, null, @2)
select [ProductID]
from [dbo].[Product]
where @@ROWCOUNT > 0 and [ProductID] = scope_identity()',N'@0 nvarchar(12),@1 decimal(18,0),@2 datetime',@0=N'I  lOVER YOU',@1=12,@2='2012-03-15 23:05:21.860'
go

                 */