The question is confusing, but it is much more clear as described in the following codes:
List<List<T>> listOfList;
// add three lists of List<T> to listOfList, for example
/* listOfList = new {
{ 1, 2, 3}, // list 1 of 1, 3, and 3
{ 4, 5, 6}, // list 2
{ 7, 8, 9} // list 3
};
*/
List<T> list = null;
// how to merger all the items in listOfList to list?
// { 1, 2, 3, 4, 5, 6, 7, 8, 9 } // one list
// list = ???
Not sure if it possible by using C# LINQ or Lambda?
Essentially, how can I concatenate or "flatten" a list of lists?
Here's the C# integrated syntax version:
var items =
from list in listOfList
from item in list
select item;
For List<List<List<x>>>
and so on, use
list.SelectMany(x => x.SelectMany(y => y)).ToList();
This has been posted in a comment, but it does deserves a separate reply in my opinion.
Do you mean this?
var listOfList = new List<List<int>>() {
new List<int>() { 1, 2 },
new List<int>() { 3, 4 },
new List<int>() { 5, 6 }
};
var list = new List<int> { 9, 9, 9 };
var result = list.Concat(listOfList.SelectMany(x => x));
foreach (var x in result) Console.WriteLine(x);
Results in: 9 9 9 1 2 3 4 5 6
Source: Stackoverflow.com