How to Union List<List<String>> in C#

Question

I'm having a List<List<String>>, and which contains

{  {"A" , "B" }, 
   {"C" , "D" }
}

I need to union all the innerlist into another list

So the resulting List<String> will contain

     {"A","B","C","D"}

Now im using for loop to do this

Is there any way to do this Using LINQ or Lambda Expression.

Please help me to do this.

Thanks in advance.

Answer 1

Not Exactly a Union, but you can try this

YourList.SelectMany(l=>l).Distinct()

Answer 2

List<List<string>> collections = new List<List<string>>()
        {
          new List<string>(){"A" , "B" }, 
          new List<string>() {"C" , "D" }
        };

var list = collections.SelectMany(x => x).ToList();

SelectMany builds up a expression tree that when evaluated flattens the list of list to a single list of combined members.

ToList forces the expression tree to be evaluated and which results in a List.

If you want to eliminate duplicates you can add a Distinct call before the call to 'ToList()'

Answer 3

You can use the SelectMany extension method.

List<List<String>> masterList = { {"A" , "B" }, {"C" , "D" } };

IEnumerable<string> results = masterList.SelectMany(l => l);