Combining lists into an arraylist (C#)

Question

I have a list and I want to copy three other lists into it.

// The main list
List<List<string>> list= new List<List<string>>();

// The lists which I want to combine
ArrayList sublist1= new ArrayList();;
ArrayList sublist2= new ArrayList();;
ArrayList sublist3= new ArrayList();;

What I tried is:

list[0].AddRange(sublist1);
list[0].AddRange(sublist2);
list[0].AddRange(sublist3);

It doesn't work because It is multidimensional list. I need this type of list for the future plans.

How can I accomplist it?

I suspect it doesn't work for other reasons (not creating instances, missing type-specificity, adding sublist2 twice, etc).. what is the real code and what is the error message / exception / incorrect result / unexplained observed behavior? (And what is the desired result?) — user166390
– user166390, Commented Aug 7, 2012 at 1:37
It says The best overloaded method match for 'System.Collections.Generic.List<string>.AddRange(System.Collections.Generic.IEnumerable<string>)' has some invalid arguments — Ned
– Ned, Commented Aug 7, 2012 at 1:41
So there you have it. You need to pass in something conforming to IEnumerable<string>. ArrayList does not. Nothing to do with multidimensionalisms. Perhaps: list[0].AddRange(sublist1.Cast<string>()) (make sure to "using" Linq) .. or better, well-type the "sublists" (e.g. List<string> sublist1 = ..). — user166390
– user166390, Commented Aug 7, 2012 at 1:41
Yes it worked! thanks @pst but I can't vote your comment for some reason — Ned
– Ned, Commented Aug 7, 2012 at 3:00

pabdulin · Accepted Answer · 2012-08-07 03:03:29Z

1

As already mentioned in comments just use List<string> instead of ArrayList. It has nothing to do about multidimensional arrays, just types mismatch.

Then you say List<List<string>> it basically means create list type, which will contain List<string> as items (the part in angle brackets), so you need to add them, not ArrayLists. Similarly List<string> means type of list which will contain string as items.

edited Aug 7, 2012 at 3:03

answered Aug 7, 2012 at 1:46

pabdulin

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Comments

skub · Accepted Answer · 2012-08-07 01:52:09Z

1

As in the comments, you need to pass a type that follows IEnumerable. For example, you can change your ArrayLists to List

// The main list
List<List<string>> list = new List<List<string>>();

// The lists which I want to combine
var sublist1 = new List<string>();
var sublist2 = new List<string>();
var sublist3 = new List<string>();

list[0].AddRange(sublist1);
list[0].AddRange(sublist2);
list[0].AddRange(sublist3);

answered Aug 7, 2012 at 1:52

skub

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Dmitry Khryukin · Accepted Answer · 2012-08-07 01:53:26Z

1

change type of sublists to some IEnumerable<string> (string[] or List<string> or something else)

var sublist1 = new string[] {};
var sublist2 = new string[] {};
var sublist3 = new string[] {};

OR do cast

list[0].AddRange((IEnumerable<string>) sublist1);
list[0].AddRange((IEnumerable<string>) sublist2);
list[0].AddRange((IEnumerable<string>) sublist3);

Because you are trying to use AddRange method of System.Collections.Generic.List<T> and the signature of this method is

public void AddRange(System.Collections.Generic.IEnumerable<T> collection)

so it requires IEnumerable as a parameter.

edited Aug 7, 2012 at 1:53

answered Aug 7, 2012 at 1:48

Dmitry Khryukin

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