linq query Take() takes precedence over Distinct()?

Question

I have to select distinct 1000 records using LINQ. But when I see the query generated it takes 1000 records and applies distinct over that result.

IQueryable<TestClass> resultSet = (from w in ......).Distinct().Take(1000);

where my TestClass would be like,

public TestClass
{
public string TestPRop { get; set; }
 //..has some 20 properties
}

Any way to solve this to get distinct applied to the resultset and then take 1000 from the distinct result set?

Answer 1

Distinct will be processed before the take. Double check your Distinct is performing correctly. Here's a working example:

var dataset = new int[]
{
    1, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10
};

var query = from o in dataset select o;
var result = query.Distinct().Take(6);

// result = `1,2,3,4,5,6`

I suspect your issue is with using distinct with SQL. If that is the case, you can also use grouping to get the result you want.

var distinctById = from o in query
                   group o by o.Id into uniqueIds
                   select uniqueIds.FirstOrDefault();