C# list add element

- C# list add element at index
- C# list add element at the beginning
- C# list add element first position
- C# list add element at the end
- C# list add element if not exists
- C# list add multiple elements
- C# list string add element
- C# list add new element
- C# list add number of elements
- C# add list elements to another list
- C# add elements from one list to another
- C# linq add element to list
- C# add element to class list
- C# reflection add element to list
- C# list add n elements