why this remove method of list dosnt work?

Question

1.00/5 (1 vote)

See more:

There is a list of objects in list1. I want if each object in list1 there was in list2 too then that object will be deleted from list2.the problem is after removing, list2 still contains that object!!!

C#

 foreach (var item in list1)
{
  
if (list2.Any(x => x.Vacationfrom == item.Vacationfrom && x.VacationTo == item.VacationTo && x.WhenIsVac == item.WhenIsVac && x.TheDay == item.TheDay))
                       
        list2.Remove(item);
}

Posted 24-Feb-15 7:06am

mit62

Add a Solution

4 solutions

Solution 4

When list1 and list2 are not mixed up, just think at this: the code when you traverse the collection in not strictly specified order and modify the set or elements at the same time (add, remove) is potentially incorrect. How to you know what you are traversing after each iteration? For removal, it does not happen if you remove while traversing the elements in reverse, using integer indices and going from higher indices to lower. Isn't it obvious?

And of course, it's better to use available method or extension methods of collections, as well as LINQ: https://msdn.microsoft.com/en-us/library/bb397919.aspx[^].

—SA

Posted 24-Feb-15 9:18am

Sergey Alexandrovich Kryukov

v2

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

manchanx · Accepted Answer · 2015-02-24T07:15:00

You're trying to remove the item that comes from list1 from list2. You would have to find the actual item from list2 that matches the item from list1 and remove that:

C#

foreach (var item in list1)
{
    var item2 = list2.SingleOrDefault(x => x.Vacationfrom == item.Vacationfrom && x.VacationTo == item.VacationTo && x.WhenIsVac == item.WhenIsVac && x.TheDay == item.TheDay);
    if(item2 != null)
        list2.Remove(item2);
}

PIEBALDconsult · Accepted Answer · 2015-02-24T07:14:00

Solution 1

item is in list1; not in list2.

You might want something like list1 = list1.Except ( ... )

https://msdn.microsoft.com/en-us/library/bb336390(v=vs.110).aspx[^]

Posted 24-Feb-15 7:14am

PIEBALDconsult

Updated 24-Feb-15 7:38am

v2

Salatiel Bairros · Accepted Answer · 2015-02-24T07:26:00

Because

var item

does not exists in list2, is a list1's item. You can use a for inside a for.
For each item in list1 you look all itens in list2 and, if the current item in list1 is equal the current item in list2, you remove that item and break the internal for and go to the next loop of the first for.

why this remove method of list dosnt work?

4 solutions

Solution 2

Solution 1

Solution 3

Solution 4

Add your solution here

Preview 0