C# list add range

- C# list addrange without duplicates
- C# list add range at beginning
- C# list add range at index
- C# list addrange null
- C# list add range remove duplicates
- C# list int add range
- C# concurrent list add range
- C# sorted list add range
- C# list add unique range
- C# new list add range
- C# list add multiple ranges
- C# list add vs addrange performance
- C# list add out of range exception
- C# list add addrange