How to empty a C# list?

To empty a C# list, use the Clear() method. This method removes all elements from the list and sets the count to zero. The Clear() method is the most efficient way to empty a list as it removes all elements in a single operation.

Syntax

Following is the syntax for the Clear() method −

listName.Clear();

Parameters

The Clear() method does not take any parameters.

Return Value

The Clear() method does not return any value. It modifies the list in-place by removing all elements.

Using Clear() Method

The following example demonstrates how to empty a list using the Clear() method −

using System;
using System.Collections.Generic;

public class Program {
   public static void Main() {
      List<string> myList = new List<string>() {
         "one",
         "two",
         "three",
         "four",
         "five",
         "six"
      };
      
      Console.WriteLine("Original list:");
      foreach(string str in myList) {
         Console.WriteLine(str);
      }
      Console.WriteLine("Elements in the list = " + myList.Count);
      
      // Empty the list using Clear()
      myList.Clear();
      
      Console.WriteLine("Elements in the list after using Clear() = " + myList.Count);
      Console.WriteLine("List is now empty: " + (myList.Count == 0));
   }
}

The output of the above code is −

Original list:
one
two
three
four
five
six
Elements in the list = 6
Elements in the list after using Clear() = 0
List is now empty: True

Clear() vs Creating a New List

There are two common approaches to empty a list. Here's a comparison between them −

Example Comparing Both Approaches

using System;
using System.Collections.Generic;

public class Program {
   public static void Main() {
      // Method 1: Using Clear()
      List<int> numbers1 = new List<int> {1, 2, 3, 4, 5};
      Console.WriteLine("Before Clear(): Count = " + numbers1.Count);
      numbers1.Clear();
      Console.WriteLine("After Clear(): Count = " + numbers1.Count);
      
      // Method 2: Creating new list (less efficient)
      List<int> numbers2 = new List<int> {10, 20, 30, 40, 50};
      Console.WriteLine("Before new assignment: Count = " + numbers2.Count);
      numbers2 = new List<int>();
      Console.WriteLine("After new assignment: Count = " + numbers2.Count);
   }
}

The output of the above code is −

Before Clear(): Count = 5
After Clear(): Count = 0
Before new assignment: Count = 5
After new assignment: Count = 0

Conclusion

The Clear() method is the recommended and most efficient way to empty a C# list. It removes all elements in a single operation while maintaining the list's existing capacity, making it faster than creating a new list instance.