Store and manage data with lists

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A List<T> is a resizable, ordered collection of values that all share the same type. Unlike an array, a list can grow or shrink while your program runs, which makes it a good fit when you don't know the exact number of items ahead of time.

Creating a list

The T in List<T> stands for the type of item the list holds. For example, List<string> holds strings, and List<int> holds integers.

List<string> colors = new List<string> { "red", "green", "blue" };
List<int> scores = new List<int>();

The first line creates a list with three starting values. The second line creates an empty list that you can add items to later.

Common list operations

Lists support several built-in methods for adding, removing, and updating items.

Operation	What it does
list.Count	Returns the number of items
list.Add(value)	Adds an item to the end of the list
list.Remove(value)	Removes the first matching item
list[i] = value	Overwrites the item at index i
list.RemoveAt(i)	Removes the item at index i
list.Sort()	Sorts the list in place

List<string> colors = new List<string> { "red", "green", "blue" };

Console.WriteLine(colors.Count); // Output: 3
colors.Add("yellow");            // Adds "yellow" to the end
Console.WriteLine(colors.Count); // Output: 4

colors.Remove("red");            // Removes "red"
colors[0] = "purple";            // Replaces "green" with "purple"

Iterating over a list

Like arrays, lists work naturally with foreach loops.

List<int> scores = new List<int> { 95, 82, 76, 91 };

foreach (int score in scores)
{
    Console.WriteLine(score);
}

Output:

95
82
76
91

Tip

Avoid hardcoding index numbers when a loop variable already tells you the position. Reaching for list[2] repeatedly in your code is a sign you probably want a foreach loop instead.

Choosing between an array and a List<T>

Choose an array when:

• You know the exact number of items ahead of time, and it won't change.
• You want the most efficient, low-overhead way to store a fixed set of values.

Choose a List<T> when:

• The number of items can grow or shrink while your program runs.
• You need built-in methods like Add, Remove, or Sort, without managing the size yourself.