C# linq how to get all the first elements of a nested dynamic list?-CodePudding

I have a nested list List<list<dynamic>>, I'd like to get all the first elements of the second level and form a new List<dynamic>.

I know .first() gets the first element of a list, but how can I give multiple elements from multiple sub list?

Thanks in advance.

CodePudding user response：

try this please if you want to take the first two elements of each list, and the more elements you want you can increase the integer in the .Take().

List<List<string>> originalList = new List<List<string>>()
{
    new List<string>(){"1","1","1"},
    new List<string>(){"2","2"},    
};    

    var FirtTwoElementsList = originalList.Select(x => x.Take(2)).ToList();
    List<string> FinalList = new List<string>();
    foreach (var item in FirtTwoElementsList)
    {
       FinalList.AddRange(item.ToList<string>());
    }

CodePudding user response：

Proper and efficient way of doing this is as follows:

mainList.Select(subList => subList?.First()).OfType<dynamic>();

This will take care of null lists and null elements

If you want to select all the elements of sublists try following

mainlist.Select(subList => subList).OfType<List<dynamic>>();

This will only take care of null lists

CodePudding user response：

You can try as below -

mainList.Where(subList => subList != null && subList.Count > 0).Select(subList => subList.First()).ToList();