16

How do you loop through IQueryable and remove some elements I don't need.

I am looking for something like this

var items = MyDataContext.Items.Where(x => x.Container.ID == myContainerId);
foreach(Item item in items)
{
  if(IsNotWhatINeed(item))
    items.Remove(item); 
}

Is it possible? Thanks in advance

John Saunders
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Aximili
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5 Answers5

18

You should be able to query that further as in this 

var filtered = items.Where(itm => IsWhatINeed(itm));

Also notice the subtle change in the boolean function to an affirmative rather than a negative. That (the negative) is what the not operator is for.

Anthony Pegram
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    With such an optimistic and positive function, you can also write `items.Where(IsWhatINeed)`. – Kobi May 30 '10 at 09:58
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    The positive version of a function also eliminates the double negative scenario: `!IsNotWhatINeed()` – Adam Naylor Jan 15 '14 at 22:45
10
items = items.Where( x => !IsNotWhatINeed(x) );
Fyodor Soikin
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  • I'd like to add that in LINQ, as with all functional code, it's more preferable to get a new list from old ones by applying a filter instead of making changes to it. – chakrit May 30 '10 at 12:21
3
var items = MyDataContext.Items.Where(x => x.Container.ID == myContainerId 
    && !IsNotWhatINeed(x));

or 

var items = MyDataContext.Items.Where(x => x.Container.ID == myContainerId) 
    .Where(x=> !IsNotWhatINeed(x));
tylerl
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2

The other answers are correct in that you can further refine the query with a 'where' statement. However, I'm assuming your query is a Linq2Sql query. So you need to make sure you have the data in memory before further filtering with a custom function:

var items = MyDataContext.Items.Where(x => x.Container.ID == myContainerId)
    .ToList(); // fetch the data in memory

var itemsToRemove = items.Where(IsNotWhatINeed);

If you really want to extend the IQueryable, then the 'IsNotWhatINeed' function must be translated to something that Linq2Sql understands.

jeroenh
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  • Thanks jeroenh, could you explain or give me an example what Linq2Sql query is and what Linq2sql understands please? Thanks! – Aximili May 31 '10 at 12:21
1

Try This:

var items = YourDataContext.Items.Where(x => x.Container.ID == myContainerId 
    && !IsNotWhatYouNeed(x));
Johnny
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