LINQ计数..最佳方法 [英] LINQ Count .. best method

问题描述

我的公司刚开始使用LINQ，但我仍然对LINQ命令和SQL的抽象性(如果是一个词)有点麻烦，我的问题是

My company has just started using LINQ and I still am having a little trouble with the abstractness (if thats a word) of the LINQ command and the SQL, my question is

  Dim query = (From o In data.Addresses _
                    Select o.Name).Count

在我看来，上面的代码是SQL返回所有行，并且对IQueryable结果中的行数进行计数，所以使用

In the above in my mind, the SQL is returning all rows and the does a count on the number rows in the IQueryable result, so I would be better with

    Dim lstring = Aggregate o In data.Addresses _
    Into Count()

或者我是否在思考LINQ的工作方式?我在家中使用VB Express，所以我看不到正在发送到数据库的实际SQL(我认为)，因为我无权访问SQL Profiler

Or am I over thinking the way LINQ works ? Using VB Express at home so I can't see the actual SQL that is being sent to the database (I think) as I don't have access to the SQL profiler

推荐答案

如上所述，它们在功能上是等效的，只是使用查询语法.

As mentioned, these are functionally equivalent, one just uses query syntax.

如我的评论中所述，如果您在 LINQPad 中将以下内容作为VB语句进行评估:

As mentioned in my comment, if you evaluate the following as a VB Statement(s) in LINQPad:

Dim lstring = Aggregate o In Test _
    Into Count()

您可以在生成的SQL输出窗口中获得此信息:

You get this in the generated SQL output window:

SELECT COUNT(*) AS [value]
FROM [Test] AS [t0]

与所评估的以下VB LINQ表达式相同:

Which is the same as the following VB LINQ expression as evaluated:

(From o In Test_
    Select o.Symbol).Count

您将获得完全相同的结果.

You get the exact same result.

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