IQueryable与IEnumberable的区别
IQueryable与IEnumberable的区别一、IEnumerable接口
公开枚举器，该枚举器支持在指定类型的集合上进行简单迭代。也就是说：实现了此接口的object，就可以直接使用foreach遍历此object
二、IQueryable 接口
它继承 IEnumerable 接口，而因为.net版本加入Linq和IQueryable后，使得IEnumerable不再那么单调，变得更加强大和丰富。
三、IQueryable与IEnumberable的区别
1、IEnumerable<T> 泛型类在调用自己的SKip 和 Take 等扩展方法之前数据就已经加载在本地内存里了
2、IQueryable<T> 是将Skip ,take 这些方法表达式翻译成T-SQL语句之后再向SQL服务器发送命令，它并不是把所有数据都加载到内存里来才进行条件过滤。
四、IQueryable与IEnumberable的实例说明一
1、IEnumerable实例
var set3 = (from c in db.cms_certificateDetails select c).OrderByDescending(c => c.id).AsEnumerable()
.Skip(150).Take(10);
foreach (var cmsCertificateDetailse in set3)
{
Console.WriteLine(cmsCertificateDetailse.czry + ";" + cmsCertificateDetailse.kddh + "\\r\\n");//打印结果
}
用sql server profiler监视的sql如下
SELECT
[Extent1].[id] AS [id],
[Extent1].[kddh] AS [kddh],
[Extent1].[czry] AS [czry],
[Extent1].[yjnr] AS [yjnr],
[Extent1].[tjTime] AS [tjTime],
[Extent1].[bz] AS [bz],
[Extent1].[forId] AS [forId]
FROM [dbo].[cms_certificateDetails] AS [Extent1]
ORDER BY [Extent1].[id] DESC
2、IQueryable实例
var set4 = (from c in db.cms_certificateDetails select c).OrderByDescending(c => c.id).AsQueryable()
.Skip(150).Take(10);
foreach (var cmsCertificateDetailse in set4)
{
Console.WriteLine(cmsCertificateDetailse.czry + ";" + cmsCertificateDetailse.kddh + "\\r\\n");//打印结果
}
用sql server profiler监视的sql如下
SELECT TOP (10)
[Extent1].[id] AS [id],
[Extent1].[kddh] AS [kddh],
[Extent1].[czry] AS [czry],
[Extent1].[yjnr] AS [yjnr],
[Extent1].[tjTime] AS [tjTime],
[Extent1].[bz] AS [bz],
[Extent1].[forId] AS [forId]
FROM ( SELECT [Extent1].[id] AS [id], [Extent1].[kddh] AS [kddh], [Extent1].[czry] AS [czry], [Extent1].[yjnr] AS [yjnr], [Extent1].[tjTime] AS [tjTime], [Extent1].[bz] AS [bz], [Extent1].[forId] AS [forId], row_number() OVER (ORDER BY [Extent1].[id] DESC) AS [row_number]
FROM [dbo].[cms_certificateDetails] AS [Extent1]
) AS [Extent1]
WHERE [Extent1].[row_number] > 150
ORDER BY [Extent1].[id] DESC
五、IQueryable与IEnumberable的实例说明二
static void Main(string[] args)
{
//创建数据库访问网关
using (SchoolDBEntities schoolEntities = new SchoolDBEntities())
{
//查询的结果放入IQueryable接口的集合中
IQueryable<T_Class> classesIQue = (from c in schoolEntities.T_Class
orderby c.ID
select c).Skip<T_Class>(3).Take<T_Class>(3);
//注意这个AsEnumerable<T_Class>()在分页查询之前，先将其转换成IEnumerable类型
IEnumerable<T_Class> classesIEnu = (from c in schoolEntities.T_Class
orderby c.ID
select c).AsEnumerable<T_Class>().Skip<T_Class>(3).Take<T_Class>(3);
//因为启用了延迟加载机制，所以下面调用一下，才会真正去读取数据库
int i = 0;
foreach (var c in classesIQue)
{
i++;
}
Console.WriteLine(i);
foreach (var c in classesIEnu)
{
i++;
}
Console.WriteLine(i);
}
Console.WriteLine("OK");
Console.ReadKey();
}
最终执行的sql
1、直接返回 IQueryable类型的查询，如下图所示：