How to declare and initialize a list in C#?

A List in C# is a generic collection that stores elements in a resizable array. You can declare and initialize a List in several ways, depending on whether you want to add elements immediately or start with an empty collection.

Syntax

Following is the basic syntax for declaring a List −

List<dataType> listName = new List<dataType>();

Following is the syntax for initializing a List with values −

List<dataType> listName = new List<dataType>() {
   value1,
   value2,
   value3
};

Empty List Declaration

To declare an empty List that you can add elements to later −

using System;
using System.Collections.Generic;

class Program {
   static void Main() {
      List<string> myList = new List<string>();
      
      myList.Add("one");
      myList.Add("two");
      myList.Add("three");
      
      Console.WriteLine("List count: " + myList.Count);
      foreach (string item in myList) {
         Console.WriteLine(item);
      }
   }
}

The output of the above code is −

List count: 3
one
two
three

List Initialization with Values

You can declare and initialize a List with values in one statement using collection initializer syntax −

using System;
using System.Collections.Generic;

class Program {
   static void Main() {
      List<string> myList = new List<string>() {
         "one",
         "two",
         "three",
         "four",
         "five",
         "six"
      };
      
      Console.WriteLine("List count: " + myList.Count);
      foreach (string item in myList) {
         Console.WriteLine(item);
      }
   }
}

The output of the above code is −

List count: 6
one
two
three
four
five
six

Different Data Types in Lists

Lists can store different data types. Here's an example with integers −

using System;
using System.Collections.Generic;

class Program {
   static void Main() {
      List<int> numbers = new List<int>() { 10, 20, 30, 40, 50 };
      
      Console.WriteLine("Integer list:");
      foreach (int num in numbers) {
         Console.WriteLine(num);
      }
      
      List<bool> flags = new List<bool>() { true, false, true };
      Console.WriteLine("\nBoolean list:");
      foreach (bool flag in flags) {
         Console.WriteLine(flag);
      }
   }
}

The output of the above code is −

Integer list:
10
20
30
40
50

Boolean list:
True
False
True

Common List Methods

Conclusion

Lists in C# provide a flexible way to store collections of data with dynamic sizing. You can declare an empty List and add elements later, or initialize it with values using collection initializer syntax. Lists are strongly typed and support various data types like strings, integers, and booleans.