C# program to create a List with elements from an array

In C#, you can easily create a List<T> with elements from an existing array. The List<T> constructor accepts an IEnumerable<T> parameter, which allows you to initialize the list directly with array elements.

Syntax

Following is the syntax to create a list from an array −

List<T> listName = new List<T>(arrayName);

You can also use the ToList() extension method −

List<T> listName = arrayName.ToList();

Using List Constructor

The most straightforward way is to pass the array directly to the List<T> constructor −

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      int[] val = new int[5];
      
      // integer elements
      val[0] = 15;
      val[1] = 25;
      val[2] = 40;
      val[3] = 58;
      val[4] = 70;
      
      List<int> myList = new List<int>(val);
      
      Console.WriteLine("Elements...");
      foreach(int res in myList) {
         Console.WriteLine(res);
      }
      
      // count integer elements
      Console.WriteLine("Number of elements: " + myList.Count);
   }
}

The output of the above code is −

Elements...
15
25
40
58
70
Number of elements: 5

Using Array Initializer with List

You can also create a list directly from an array initializer −

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      int[] numbers = {10, 20, 30, 40, 50};
      List<int> numberList = new List<int>(numbers);
      
      Console.WriteLine("List created from array initializer:");
      foreach(int num in numberList) {
         Console.WriteLine(num);
      }
      
      Console.WriteLine("Total elements: " + numberList.Count);
   }
}

The output of the above code is −

List created from array initializer:
10
20
30
40
50
Total elements: 5

Using ToList() Extension Method

The ToList() method from System.Linq provides another convenient way to convert arrays to lists −

using System;
using System.Collections.Generic;
using System.Linq;

public class Demo {
   public static void Main() {
      string[] cities = {"New York", "London", "Paris", "Tokyo"};
      List<string> cityList = cities.ToList();
      
      Console.WriteLine("Cities converted to List:");
      foreach(string city in cityList) {
         Console.WriteLine(city);
      }
      
      Console.WriteLine("List count: " + cityList.Count);
   }
}

The output of the above code is −

Cities converted to List:
New York
London
Paris
Tokyo
List count: 4

Comparison of Methods

Conclusion

Creating a List<T> from an array in C# can be done using the List constructor or the ToList() extension method. The constructor approach is more direct and performs better, while ToList() offers better readability and is useful in LINQ operations.