How to find all records that have a duplicate based on a column

Question

I'm trying to construct a query in LINQ/Entity Framework that will return all rows that have a duplicate based on one column. However, I don't want to group them, I actually want to get all the rows that have the duplicate.

name age
---- ---
john 15
john 16
jack 20
jill 26
sam  10
sam  12

How can I get a list of rows that have duplicates based on the name column? This is the resultset I'm expecting:

name age
---- ---
john 15
john 16
sam  10
sam  12

I tried something like this, but I think this will give me a grouped result I think:

var duplicates = Shop.GroupBy(r => r.Name)
                     .Where(x => x.Count() > 1)
                     .Select(val => val.Key);

Answer 1

Use SelectMany:

var duplicates = Shop.GroupBy(r => r.Name)
                     .Where(x => x.Count() > 1)
                     .SelectMany(g=> g);

It will help you to flatten the result of each group that have more than one element in just one collection