How to insert an item in a list at a given position in C#?

To insert an item in an already created List, use the Insert() method. This method allows you to insert an element at a specific index position within the list, shifting all subsequent elements to the right.

Syntax

Following is the syntax for the Insert() method −

list.Insert(index, item);

Parameters

• index − The zero-based index at which the item should be inserted.

• item − The object to insert into the list.

Using Insert() Method

Firstly, create a list and add elements −

List<int> list = new List<int>();
list.Add(989);
list.Add(345);
list.Add(654);
list.Add(876);
list.Add(234);
list.Add(909);

Now, to insert an item at the 4th position (index 3), use the Insert() method −

// inserting element at index 3 (4th position)
list.Insert(3, 567);

Example

using System;
using System.Collections.Generic;

namespace Demo {
    public class Program {
        public static void Main(string[] args) {
            List<int> list = new List<int>();

            list.Add(989);
            list.Add(345);
            list.Add(654);
            list.Add(876);
            list.Add(234);
            list.Add(909);

            Console.WriteLine("Count: {0}", list.Count);

            Console.Write("List: ");
            foreach(int i in list) {
                Console.Write(i + " ");
            }
            
            // inserting element at 4th position (index 3)
            list.Insert(3, 567);
            
            Console.Write("\nList after inserting a new element: ");
            foreach(int i in list) {
                Console.Write(i + " ");
            }
            Console.WriteLine("\nCount: {0}", list.Count);
        }
    }
}

The output of the above code is −

Count: 6
List: 989 345 654 876 234 909 
List after inserting a new element: 989 345 654 567 876 234 909 
Count: 7

Insert Multiple Items at Different Positions

Example

using System;
using System.Collections.Generic;

class Program {
    public static void Main() {
        List<string> fruits = new List<string> {"Apple", "Banana", "Orange"};

        Console.WriteLine("Original list:");
        foreach(string fruit in fruits) {
            Console.Write(fruit + " ");
        }

        // Insert at the beginning (index 0)
        fruits.Insert(0, "Mango");
        
        // Insert at the end (current count)
        fruits.Insert(fruits.Count, "Grapes");
        
        // Insert in the middle (index 2)
        fruits.Insert(2, "Cherry");

        Console.WriteLine("\nAfter multiple insertions:");
        foreach(string fruit in fruits) {
            Console.Write(fruit + " ");
        }
    }
}

The output of the above code is −

Original list:
Apple Banana Orange 
After multiple insertions:
Mango Apple Cherry Banana Orange Grapes

Key Points

• The Insert() method uses zero-based indexing, so index 0 is the first position.

• Elements at and after the insertion index are shifted to the right.

• The list's Count property increases by 1 after insertion.

• You can insert at index 0 (beginning) or at the current count (end).

Conclusion

The Insert() method provides a convenient way to add elements at specific positions in a C# List. It automatically handles shifting existing elements and updating the list size, making it easy to maintain ordered collections.