Combining lists into an arraylist (C#) - list

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?

Answer 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.

Answer 2

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);

Answer 3

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.