Finding duplicate row using Linq

Question

Person

Name        City

Joe         Houston   
Jerry       London    
Alex        Houston   
Jerry       London

How to return duplicate row using LINQ like

Sql

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

I tried something

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

Jon Skeet · Accepted Answer · 2009-12-11 19:45:36Z

14

You need a where, not a select:

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

answered Dec 11, 2009 at 19:45

Jon Skeet

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1 Comment

altandogan Over a year ago

Hi John,I want to ask question. Is it possible to select duplicate rows key and value?

CodingYourLife · Accepted Answer · 2021-01-10 21:43:16Z

1

Building on @Jon Skeet's answer with a "one liner" alternative that returns the duplicate values, not just the keys:

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

edited Jan 10, 2021 at 21:43

CodingYourLife

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answered Feb 17, 2018 at 12:54

Jorge Rodrigues dos Santos

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