Take all in ternary operator in LINQ?

Question

Consider this function :

public List<Employees> getEmployees(....... , int? takeMax = null)
{
    // some code 
    ...

    var items = DB_Context.Employees.Where(%%%%% WHATEVER %%%%).Take(takeMax.HasValue && takeMax.Value > 0 ? takeMax.Value :  ?????? ).ToList();
}

How can I take all the items in case takeMax is NULL?

The Take() takes int , and I don't want to write something like

int total = DB_Context.Employees.Count();
var items = DB_Context.Employees.Where(%%%%% WHATEVER %%%%).Take(takeMax.HasValue && takeMax.Value > 0 ? takeMax.Value :  total ).ToList();

Any alternative ?

You might want to add braces to your condition & check. It works fine for me without any error — Nikita Shrivastava, Oct 08 '15 at 08:08

TomDoesCode · Answer 1 · 2015-10-08T08:12:08.600

4

You could only apply the take in that case:

var itemsQuery = DB_Context.Employees.Where(%%%%% WHATEVER %%%%);
if (takeMax > 0)
{
  itemsQuery  = itemsQuery.Take(takeMax);
}

var items = itemsQuery.ToList();

edited Oct 08 '15 at 08:12

answered Oct 08 '15 at 07:58

TomDoesCode

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Even better than mine(now deleted) `if...else` approach. Both use the same `Where`. – Tim Schmelter Oct 08 '15 at 08:03
I might not suggest this because I might want only 10 rows out of thousands in the db. I shouldn't be retreiving all of them. – Nikita Shrivastava Oct 08 '15 at 08:03
@TimSchmelter Take() is used when you do not want to retreive everything(SELECT TOP n) , so I would prefer to have filtered records at the time of fetching & not after it(getting all the records & then Take()) – Nikita Shrivastava Oct 08 '15 at 08:05
1

You don't need the `HasValue` part [read this](http://stackoverflow.com/questions/15777745/how-does-comparison-operator-works-with-null-int) – Bobby Tables Oct 08 '15 at 08:06
4

@Nikita: i guess you don't have understood LINQ's deferred execution. The query is not executed in the first line but in the last line. – Tim Schmelter Oct 08 '15 at 08:07
@TimSchmelter I just tried it and it was fine. See the link that toby provided. – TomDoesCode Oct 08 '15 at 08:09
@TimSchmelter Oh, I totally missed that..thanks for pointing out ! – Nikita Shrivastava Oct 08 '15 at 08:10
It should be `takeMax > 0`, If you access the value property you'll an error – Bobby Tables Oct 08 '15 at 08:11

Arghya C · Accepted Answer · 2015-10-08T08:07:10.513

3

This is a way, where you still have to write two lines (like your example of taking count), but you do not have to calculate Count.

var query = DB_Context.Employees.Where(%%%%% WHATEVER %%%%);
var items = takeMax.HasValue && takeMax.Value > 0 ? 
                query.Take(takeMax.Value).ToList() : query.ToList();

edited Oct 08 '15 at 08:07

answered Oct 08 '15 at 08:01

Arghya C

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You mean that the evaluation of the query would be done in the second line , right ? Nice one . – JAN Oct 08 '15 at 08:04
@ron Yes, until you do a `ToList()` or `foreach`, the query is not evaluated. – Arghya C Oct 08 '15 at 08:05

score 0 · Answer 3 · answered Oct 08 '15 at 07:59

Maybe like this:

public List<Employees> getEmployees(....... , int? takeMax = null)
{
// some code 


...

if(takeMax != null)
{
    return DB_Context.Employees.Where(%%%%% WHATEVER %%%%).Take(takeMax).ToList();
}
else
{
    return return DB_Context.Employees.Where(%%%%% WHATEVER %%%%).ToList();
}

Take all in ternary operator in LINQ?

3 Answers3