Conditional foreach

Question

I have

class Item
{
    public string Id {get;set;}
}

and this code

public void(List<string> sd)        
{
    List<Item> newitems = new List<Item>();
    foreach(var item in sd)
    {
        newItems.Add(new Item { Id = item});
    }
}

If sd contains more than ten items I should create new object List<Item> and initialize it by values from 11 item.

How much better to do it?

Your question is not very clear. Do you want to create multiple lists? i.e., you want to have `List>`? — Yacoub Massad, Dec 12 '15 at 13:19

score 1 · Answer 1 · edited May 23 '17 at 12:15

It seems that you want to create lists of Item from a list of string, you can use Select() to create a list instead of foreach. Then, you just need to split the list into sublists:

var allItems = sd.Select(id => new Item { Id = id });
var subLists = Split(allItems);

You can use the Split() method in this answer:

public static List<List<object>> Split(List<object> source)
{
    return source
        .Select((x, i) => new { Index = i, Value = x })
        .GroupBy(x => x.Index / 10)
        .Select(x => x.Select(v => v.Value).ToList())
        .ToList();
}

Andrew Cheong · Answer 2 · 2015-12-12T20:31:24.670

I'm a C++ programmer so forgive any bad syntax, but this is where you can use a reference to a currentList that varies as you create a new list each time one fills up, using an if condition within your foreach.

public void(List<string> sd)        
{
    // Create a list of lists to store your lists.
    List<List<Item>> lists;

    // We're going to use this variable to refer to our
    // current, not-yet-full list (less than 10 items).
    List<Item> currentList;

    // Create the first list you'll be adding items to,
    // and add it to our list of lists.
    currentList = new List<Item>();
    lists.Add(currentList);

    foreach(var item in sd)
    {
        currentList.Add(new Item { Id = item});

        if(currentList.Count() >= 10)
        {
            // This should look familiar from above :-)
            currentList = new List<Item>();
            lists.Add(currentList);
        }
    }
}

If I've got some syntax wrong, please feel free to edit and correct my answer.

Conditional foreach

2 Answers2