IQueryable與IEnumberable的差別有哪些



一、IEnumerable接口

公開枚舉器，該枚舉器支援在指定類型的集合上進行簡單疊代。也就是說：實作了此接口的object，就可以直接使用foreach周遊此object

二、IQueryable 接口

它繼承 IEnumerable 接口，而因為.net版本加入Linq和IQueryable後，使得IEnumerable不再那麼單調，變得更加強大和豐富。

三、IQueryable與IEnumberable的差別

1、IEnumerable<T> 泛型類在調用自己的SKip 和 Take 等擴充方法之前資料就已經加載在本地記憶體裡了

2、IQueryable<T> 是将Skip ,take 這些方法表達式翻譯成T-SQL語句之後再向SQL伺服器發送指令，它并不是把所有資料都加載到記憶體裡來才進行條件過濾。

四、IQueryable與IEnumberable的執行個體說明一

1、IEnumerable執行個體

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");//列印結果
}
           

生成的SQL 語句

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執行個體

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");//列印結果
}
           

生成的SQL語句

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
           

文章轉載自：   IQueryable與IEnumberable的差別   http://www.studyofnet.com/news/730.html