CODEWITHSUNDEEP
c#list
Robert
Robert

Reputation: 4406

How to find current index of your list / array in a changing list?

I have a list of lets say 10 items on the first call:

 var myList = GetMyList();

okay now I get the item I want from this list:

 myList.FirstOrDefault(x => x.Id == id);

Now I go to the web page and do stuff.

Now I am back: The list Could have changed by this point if anything was deactivated through a rest call in my API. (I rebuild the current list in the constructor)

public OneItemFromMyList Get(int id)
{
     //Here I need the next item in the list after the one with the above Id
}

So how do I get that one. I do not want to repeat one that I retrieved before and I don't want to move outside of the list so I would need to start over if I am on the last position.

Any Suggestions?

Upvotes: 1

Views: 69

Answers (2)

Enigmativity
Enigmativity

Reputation: 117134

I think this will work for you:

var nextId =
    myList
        .SkipWhile(x => x != id) //skip until x == id
        .Skip(1) // but I don't want x == id so skip one more
        .Concat(myList) // but item could be removed or I hit the end so restart
        .First(); // the first item is the one I want!

Upvotes: 1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726849

To get an item immediately after the one with the specific id, do this:

var nextItem = myList.SkipWhile(x => x.Id != id).Take(2).LastOrDefault();

Note that this may not produce an item, if either of the following is true:

  • The item with x.Id == id is not there, or
  • The item with x.Id == id is the last item in the list.

Upvotes: 1

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