Array of string from Arraylist of Arraylist

Question

I want to create an array of string from Arraylist of Arraylist.

Here is a code:

ArrayList MainList = new ArrayList();

ArrayList subList = new ArrayList();
subList.Add("A");
subList.Add("Apple");
MainList.Add(subList);

subList = new ArrayList();
subList.Add("B");
subList.Add("Banana");
MainList.Add(subList);

subList = new ArrayList();
subList.Add("C");
subList.Add("Caret");
MainList.Add(subList);

string[] AllList = { "A", "Apple", "B", "Banana", "C", "Caret" };
string[] OnlySome = { "Apple", "Banana", "Caret" };

I know we can do it using for each loop but how can I get AllList and OnlySome string array using LINQ Query ?

Thanks

Is there any particular reason you're using ArrayList instead of List<T>? — Gabe
– Gabe, Commented Mar 24, 2011 at 16:04
I'd also recommend you don't store your subLists as ArrayList. It seems more likely that you should be using something like: Dictionary<string,string>, List<FruitLookup>, List<KeyValuePair<string,string>> or maybe a List<Tuple<string,string>> — Stuart
– Stuart, Commented Mar 24, 2011 at 16:43

Anton Gogolev · Accepted Answer · 2011-03-24 16:08:22Z

3

Sure:

var allList = 
    MainList.
        Cast<ArrayList>().
        SelectMany(a => a.Cast<string>()).
        ToArray();

var onlySome = 
    MainList.
        Cast<ArrayList>().
        Select(a => 
            a.Cast<string>().
                Skip(1).
                First()).
        ToArray();

answered Mar 24, 2011 at 16:08

Anton Gogolev

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1 Comment

user1228 Over a year ago

I'm not sure if Cast or OfType is better in cases like this. I do prefer to Cast when casting, and to use OfType when I know the collection contains elements of that type and that they are all I care about.

Sanjeevakumar Hiremath · Accepted Answer · 2011-03-24 19:16:26Z

0

I wasn't sure what was the exact condition for OnlySome, therefore I thought 2 options,

Select every other element (odd indexed, even location) onlySome1

Select any string which has a length greater than 1 onlySome2

    var allList = (from al in MainList.ToArray()
                  from s in (al as ArrayList).ToArray()
                  select s as string).ToArray();

    // if you want to select every other element
    var onlySome1 = allList.Where((s, index) => index % 2 == 1).ToArray();

    // if you want to select all the strings with 2 or more characters.
    var onlySome2 = allList.Where(s => (s as string).Length > 1).ToArray();

edited Mar 24, 2011 at 19:16

answered Mar 24, 2011 at 18:41

Sanjeevakumar Hiremath

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