c# - Get distinct records using linq to entity

Question

Hi I'm using linq to entity in my application. I need to get distinct records based on one column value "Name"

So I have a table similar like you can see below:

(User)
ID
Name
Country
DateCreated

I need to select all this items but uniques based on Name (unique). Is it possible to accomplish using linq, if so please show me how.

var items = (from i in user select new  {i.id, i.name, i.country, i.datecreated}).Distinct();

Answer 1

The Distinct() method doesn't perform well because it doesn't send the DISTINCT SQL predicate to the database. Use group instead:

var distinctResult = from c in result
             group c by c.Id into uniqueIds
             select uniqueIds.FirstOrDefault();

LINQ's group actually creates subgroups of entities keyed by the property you indicate:

Smith
  John
  Mary
  Ed
Jones
  Jerry
  Bob
  Sally

The syntax above returns the keys, resulting in a distinct list. More information here:

http://imar.spaanjaars.com/546/using-grouping-instead-of-distinct-in-entity-framework-to-optimize-performance