Remove a range of elements from the List in C#

The RemoveRange() method in C# allows you to remove multiple elements from a List<T> at once by specifying a starting index and the number of elements to remove. This is more efficient than removing elements one by one.

Syntax

Following is the syntax for the RemoveRange() method −

public void RemoveRange(int index, int count)

Parameters

• index − The zero-based starting index of the range of elements to remove.

• count − The number of elements to remove starting from the specified index.

Using RemoveRange() to Remove Multiple Elements

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(String[] args) {
      List<string> countries = new List<string>();
      countries.Add("India");
      countries.Add("US");
      countries.Add("UK");
      countries.Add("Canada");
      countries.Add("Poland");
      countries.Add("Netherlands");

      Console.WriteLine("Original List:");
      foreach (string country in countries) {
         Console.WriteLine(country);
      }

      Console.WriteLine("\nCount before removal: " + countries.Count);

      // Remove 3 elements starting from index 1 (US, UK, Canada)
      countries.RemoveRange(1, 3);

      Console.WriteLine("Count after removal: " + countries.Count);
      Console.WriteLine("\nUpdated List:");
      foreach (string country in countries) {
         Console.WriteLine(country);
      }
   }
}

The output of the above code is −

Original List:
India
US
UK
Canada
Poland
Netherlands

Count before removal: 6
Count after removal: 3

Updated List:
India
Poland
Netherlands

Multiple RemoveRange() Operations

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(String[] args) {
      List<string> list = new List<string>();
      list.Add("India");
      list.Add("US");
      list.Add("UK");
      list.Add("Canada");
      list.Add("Poland");
      list.Add("Netherlands");
      list.Add("Bhutan");
      list.Add("Singapore");

      Console.WriteLine("Original List:");
      foreach (string item in list) {
         Console.WriteLine(item);
      }

      Console.WriteLine("\nFirst RemoveRange(1, 3):");
      list.RemoveRange(1, 3);
      Console.WriteLine("Count: " + list.Count);
      foreach (string item in list) {
         Console.WriteLine(item);
      }

      Console.WriteLine("\nSecond RemoveRange(2, 2):");
      list.RemoveRange(2, 2);
      Console.WriteLine("Count: " + list.Count);
      foreach (string item in list) {
         Console.WriteLine(item);
      }
   }
}

The output of the above code is −

Original List:
India
US
UK
Canada
Poland
Netherlands
Bhutan
Singapore

First RemoveRange(1, 3):
Count: 5
India
Poland
Netherlands
Bhutan
Singapore

Second RemoveRange(2, 2):
Count: 3
India
Poland
Singapore

Key Points

• The RemoveRange() method modifies the original list by removing the specified elements.

• Elements after the removed range are shifted to fill the gap, maintaining the list's contiguous structure.

• If the starting index or count parameters are invalid, an ArgumentOutOfRangeException is thrown.

• This method is more efficient than calling Remove() multiple times for consecutive elements.

Conclusion

The RemoveRange() method provides an efficient way to remove multiple consecutive elements from a List<T> in a single operation. It requires specifying the starting index and the number of elements to remove, making it ideal for bulk deletion operations.