Option #1: Use Clear() function to empty the List<T> and retain it's capacity.
Count is set to 0, and references to other objects from elements of the collection are also released.
Capacity remains unchanged.
Option #2 - Use Clear() and TrimExcess() functions to set List<T> to initial state.
Count is set to 0, and references to other objects from elements of the collection are also released.
Trimming an empty
List<T>sets the capacity of the List to the default capacity.
Definitions
Count = number of elements that are actually in the List<T>
Capacity = total number of elements the internal data structure can hold without resizing.
Clear() Only
List<string> dinosaurs = new List<string>();
dinosaurs.Add("Compsognathus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Deinonychus");
Console.WriteLine("Count: {0}", dinosaurs.Count);
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
dinosaurs.Clear();
Console.WriteLine("\nClear()");
Console.WriteLine("\nCount: {0}", dinosaurs.Count);
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Clear() and TrimExcess()
List<string> dinosaurs = new List<string>();
dinosaurs.Add("Triceratops");
dinosaurs.Add("Stegosaurus");
Console.WriteLine("Count: {0}", dinosaurs.Count);
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
dinosaurs.Clear();
dinosaurs.TrimExcess();
Console.WriteLine("\nClear() and TrimExcess()");
Console.WriteLine("\nCount: {0}", dinosaurs.Count);
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);