Pranay Rana: Find duplicate with Linq

Thursday, March 3, 2011

Find duplicate with Linq

In this small post I am going to discuss about how to get list of duplicate items for the collection that we do in sql.
For example I have to get list of the email id which is get entered in user table more than one time.
SELECT email, 
  COUNT(email) AS NumOccurrences
FROM users
GROUP BY email
HAVING ( COUNT(email) > 1 )
Linq query work same as on the set of collection and which make use of count
DataClassesDataContext db = new DataClassesDataContext();
var duplicates = db.Users
    .GroupBy(i => i.emailid)
    .Where(g => g.Count() > 1)
    .Select(g => g.emailid);
foreach (var d in duplicates)
So by using above query you can easily achieve task of finding duplicate for your set of collection.

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