如何在LINQ中组合Where子句和group by [英] How to combine Where clause and group by in LINQ

问题描述

任何人都可以帮助我将下面的代码转换为LINQ吗?

Can any one help me convert the below code to LINQ?

Select Catg,Count(*)  From Mycatg  where IsPublic=1 or FirstName='XXX' Group By Catg  .

推荐答案

在C#中，类似:

var query = from category in mycatg
            where category.IsPublic == 1
               || category.FirstName == "XXX"
            group 1 by category.Catg into grouped
            select new { Catg = grouped.Key,
                         Count = grouped.Count() };

"1"的投影清楚地表明，我们需要的只是分组和计数的关键-每个分组中的各个条目都是不相关的.

The projection of "1" makes it clear that all we need is the key of the grouping and the count - the individual entries in each grouping are irrelevant.

使用lambda语法和点表示法:

Using lambda syntax and dot notation:

var query = mycatg.Where(category => category.IsPublic == 1
                         || category.FirstName == "XXX")
                  .GroupBy(category => category.Catg,
                           category => 1)
                  .Select(grouped => new { Catg = grouped.Key,
                                           Count = grouped.Count() });

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