IQueryable接口與IEnumberable接口的區別

簡單解釋一下：從網上看到IQueryable接口與IEnumberable接口的區別，都是簡單的說了一下下面第一點的緣由，沒有實際的代碼，我就簡單的在敘述一下其區別的詳細的過程。 

1：這是從網上找的區別的緣由，好多都是這一樣的解釋：

IEnumerable<T> 泛型類在調用本身的SKip 和 Take 等擴展方法以前數據就已經加載在本地內存裏了，而IQueryable<T> 是將Skip ,take 這些方法表達式翻譯成T-SQL語句以後再向SQL服務器發送命令，它並非把全部數據都加載到內存裏來才進行條件過濾。

2：我設置一個查詢，代碼以下：

//返回IEnumerable開始

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");//打印結果
}

用sql server profiler監視的sql以下：

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

 //返回IEnumerable結束

 

 //返回IQueryable開始

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");//打印結果
}

用sql server profiler監視的sql以下：

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

 //返回IQueryable結束

 

3：這下就看出來了，返回IQueryable類型的方法，執行條件查詢是放到數據庫中的，返回到內存的數據是已通過濾的，然而返回IEnumerable類型的方法，執行條件確定是從內存中進行過濾的,返回到內存的數據是沒有通過過濾的！