復制代碼 代碼如下:

SELECT COUNT(*) AS [value]
FROM (
SELECT
(CASE
WHEN ([t1].[CompanyID] = ([t0].[ID])) AND ([t1].[IsDeleted] = @p0) AND (([t1].[AuditStatus] = @p1) OR ([t1].[AuditStatus] = @p2)) THEN 1
WHEN NOT (([t1].[CompanyID] = ([t0].[ID])) AND ([t1].[IsDeleted] = @p0) AND (([t1].[AuditStatus] = @p1) OR ([t1].[AuditStatus] = @p2))) THEN 0
ELSE NULL
END) AS [value]
FROM [Company_Product_Maintain] AS [t1]
) AS [t2]
WHERE [t2].[value] = 1

復制代碼 代碼如下:

SELECT COUNT(*) AS [value]
FROM [GasSNS_Company_Equipment_Maintain] AS [t1]
WHERE ([t1].[CompanyID] = ([t0].[ID])) AND ([t1].[IsDeleted] = @p0) AND (([t1].[AuditStatus] = @p1) OR ([t1].[AuditStatus] = @p2))

 圖1為Count結果，用了35秒，哇塞！

圖2為Where(條件).Count()結果，同樣的數據只用了4秒鐘，差了10倍！

然后為了取值方面我還是加入三元運算，ContentStatus=Product_Maintain.Where(C => C.CompanyID == company.ID && C.IsDeleted == 0 && (C.AuditStatus == 0 || C.AuditStatus == 4)).Count()>0？"產品有更新":""。結果如下：

真的是Count()與 Where()區別，不可能這么大差距吧？于是我單寫

 Product_Maintain.Where(C => C.IsDeleted == 0 && (C.AuditStatus == 0 || C.AuditStatus == 4)).Count()  與

 Product_Maintain.Count(C => C.IsDeleted == 0 && (C.AuditStatus == 0 || C.AuditStatus == 4))   

發現速度差不多，生成的代碼是一樣的。

復制代碼 代碼如下:

SELECT COUNT(*) AS [value]
FROM [GasSNS_Company_Equipment_Maintain] AS [t0]
WHERE ([t0].[IsDeleted] = @p0) AND (([t0].[AuditStatus] = @p1) OR ([t0].[AuditStatus] = @p2))

復制代碼 代碼如下:

//效率低版本：
from company in Company
select new
{
contacter = v.ContacterID,
count = Product_Maintain.Count(C => C.CompanyID == company.ID &&C.IsDeleted == 0 && (C.AuditStatus == 0 || C.AuditStatus == 4))
}

復制代碼 代碼如下:

//效率高版本：
from company in Company
select new
{
contacter = v.ContacterID,
count = Product_Maintain.Where(C =>C.CompanyID == company.ID && C.IsDeleted == 0 && (C.AuditStatus == 0 || C.AuditStatus == 4)).Count()
}

      總結到此，望各位看官以后要注意！本人入園兩年來，第一發在首頁，請各位看官不吝賜教！

      謝謝各位看官的指點，聲明下以上查詢圖都LinqPad查詢結果截圖。至于為啥4秒左右為LinqPad查詢時間，Linq生成Sql語句在Sql Server中執行不到1秒，以下截圖作解釋：