Remove an item from a LINQ collection

Question

I think I am putting my question correctly :)

I am querying the database using LINQ to retrieve some data. Please find the code below.

var leadtasktype = _context.LeadTypeTaskTypes.Where(l => l.LeadTypeId == item.Value);

foreach(LeadTypeTaskType l in leadtasktype){
    if (l.TaskTypeId == 21)
    {
        //I need to remove an item which has the tasktype id 21
    }
}

As I mentioned in the comments, I need to remove items from the leadtasktype based on my if condition. How do I do this?

Look at this answer: http://stackoverflow.com/questions/853526/using-linq-to-remove-objects-within-a-listt — Niklas Wulff, Nov 08 '12 at 13:26

score 5 · Answer 1 · answered Nov 08 '12 at 13:23

5

This would seem very like another filter condition:

var leadtasktype = _context.LeadTypeTaskTypes
    .Where(l => l.LeadTypeId == item.Value)
    .Where(l => l.TaskTypeId != 21); // Exclude ID = 21.

answered Nov 08 '12 at 13:23

Paul Turner

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score 3 · Answer 2 · answered Nov 08 '12 at 13:24

3

Just leave them out of your set:

var leadtasktype = _context.LeadTypeTaskTypes
    .Where(l => 
        l.leadTypeId != 21 && 
        l.LeadTypeId == item.Value
    );

answered Nov 08 '12 at 13:24

Alex

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It's also worth pointing out that for LINQ to Objects this approach is slightly faster than chaining `.Where()` methods, since less iterators are going to be used. For LINQ to SQL on the other hand, the same SQL code should be generated so it makes no real difference apart from style and readability (I myself like chaining better). – Alex Nov 09 '12 at 07:49

score 3 · Accepted Answer · answered Nov 08 '12 at 13:24

3

var leadtasktype = _context.LeadTypeTaskTypes.Where(l => l.LeadTypeId == item.Value && l.LeadTypeId != 21);

answered Nov 08 '12 at 13:24

Alex Kovanev

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Lukas Winzenried · Answer 4 · 2012-11-09T14:10:18.833

2

var leadtasktype = _context.LeadTypeTaskTypes
    .Where(l => l.LeadTypeId == item.Value 
                && l.TaskTypeId != 21); // Exclude ID = 21.

edited Nov 09 '12 at 14:10

answered Nov 08 '12 at 13:25

Lukas Winzenried

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score 2 · Answer 5 · edited Nov 08 '12 at 13:41

2

Is it this what you want ?

var leadtasktype = _context.LeadTypeTaskTypes.RemoveAll
   (l => l.LeadTypeId == item.Value && l.LeadTypeId == 21);

edited Nov 08 '12 at 13:41

m4ngl3r

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answered Nov 08 '12 at 13:34

Henrik Bøgelund Lavstsen

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m4ngl3r · Answer 6 · 2012-11-08T13:35:38.977

1

var leadtasktype = _context.LeadTypeTaskTypes.Where(l => l.LeadTypeId == item.Value);

var newData = leadtasktype;

                foreach(LeadTypeTaskType l in leadtasktype){
                    if (l.TaskTypeId == 21)
                    {
                        newData.Remove(l);
                    }
                }

edited Nov 08 '12 at 13:35

answered Nov 08 '12 at 13:23

m4ngl3r

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You cannot modify a collection in a `foreach` loop. – Sani Huttunen Nov 08 '12 at 13:23
3

o please forgive me for this, Colorado and Washington just have passed the Marijuana legalization... so i feel a little bit high now.. = } – m4ngl3r Nov 08 '12 at 13:32

score 1 · Answer 7 · answered Nov 08 '12 at 13:25

1

var leadtasktype = _context.LeadTypeTaskTypes.Where(l => l.LeadTypeId == item.Value);

for (var i = 0; i < leadtasktype.Count; i++)
{
  if (leadtasktype[i].TaskTypeId == 21)
  {
    leadtasktype.RemoveAt(i);
  }
}

answered Nov 08 '12 at 13:25

Sani Huttunen

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you should not do that. this will kill your performance on large lists. – Lukas Winzenried Nov 08 '12 at 13:28

Remove an item from a LINQ collection

7 Answers7