Question

人

Name              City

Joe         Houston   
Jerry       London    
Alex        Houston   
Jerry       London

如何使用LINQ返回重复行，如

的Sql

SELECT name, city, count(*)
FROM collection
GROUP BY name,city 
HAVING count(*) > 1

我尝试了一些东西

var qry =
                from m in context.Collections
                group m by new { m.city, m.name } into grp
                select new { rp = grp.Count() > 2 };

Answer 1

你需要一个地方，而不是一个选择：

var qry =  from m in context.Collections
           group m by new { m.city, m.name } into grp
           where grp.Count() > 1
           select grp.Key;

Answer 2

以 @Jon Skeet 的答案为基础，使用“one liner”替代方案，返回重复值，而不仅仅是键：

var duplicates = db.Collections.GroupBy(a => new { m.city, m.name })
                               .Where(a => a.Count() > 1)
                               .SelectMany(a => a.ToList());

C＃Linq找到重复的行

2 个答案: