IList<T> Interface (System.Collections.Generic)

IList<T> Interface

Assembly: System.Runtime.dll

Represents a strongly typed collection of objects that can be individually accessed by index. The most base interface for collections that can be accessed by index.

Remarks

The IList<T> interface inherits from the ICollection<T> interface, which in turn inherits from the IEnumerable<T> interface.

An IList<T> can be accessed by an integer index. The elements are zero-based.

This interface supports the following operations:

Adding elements.
Removing elements.
Inserting elements.
Accessing elements by index.
Searching for elements.

The implementations of IList<T> can be read-only, in which case they throw an NotSupportedException if an attempt is made to add or remove elements.

Inheritance Hierarchy

System.Object
System.Collections.Generic.IEnumerable<T>
System.Collections.ICollection
System.Collections.Generic.ICollection<T>
System.Collections.Generic.IList<T>

Members

Properties

Name	Description
`Count`	Gets the number of elements contained in the `ICollection<T>`. (Inherited from `ICollection<T>`)
`IsFixedSize`	Gets a value indicating whether the `IList` has a fixed size.
`IsReadOnly`	Gets a value indicating whether the `ICollection<T>` is read-only. (Inherited from `ICollection<T>`)
`Item[Int32]`	Gets or sets the element at the specified index.

Methods

Name	Description
`Add(T element)`	Adds an item to the end of the `IList<T>`.
`Clear()`	Removes all items from the `ICollection<T>`. (Inherited from `ICollection<T>`)
`Contains(T element)`	Determines whether the `ICollection<T>` contains a specific value. (Inherited from `ICollection<T>`)
`CopyTo(T[] array, Int32 arrayIndex)`	Copies the entire `ICollection<T>` to a compatible one-dimensional `Array`, starting at the specified array index. (Inherited from `ICollection<T>`)
`IndexOf(T element)`	Determines the zero-based index of the first occurrence of a value in the `IList<T>`.
`Insert(Int32 index, T element)`	Inserts an item at the specified position in the `IList<T>`.
`Remove(T element)`	Removes the first occurrence of a specific object from the `ICollection<T>`. (Inherited from `ICollection<T>`)
`RemoveAt(Int32 index)`	Removes the `IList<T>` item at the specified index.

Explicit Interface Implementations

Interface	Name	Description
`System.Collections.IList`	`System.Collections.IList.Add(Object value)`	Adds an `Object` to the `IList`.
`System.Collections.IList`	`System.Collections.IList.Contains(Object value)`	Determines whether an element is in the `IList`.
`System.Collections.IList`	`System.Collections.IList.IndexOf(Object value)`	Determines the zero-based index of the first occurrence of a value that matches the object.
`System.Collections.IList`	`System.Collections.IList.Insert(Int32 index, Object value)`	Inserts an element into the `IList` at the specified index.
`System.Collections.IList`	`System.Collections.IList.Remove(Object value)`	Removes the first occurrence of the specified `Object` from the `IList`.
`System.Collections.IList`	`System.Collections.IList.RemoveAt(Int32 index)`	Removes the element at the specified index from the `IList`.

Examples

C# Example


using System;
using System.Collections.Generic;

public class Example
{
    public static void Main(string[] args)
    {
        // Create a list of strings using the IList interface
        IList<string> stringList = new List<string>();

        // Add elements
        stringList.Add("Apple");
        stringList.Add("Banana");
        stringList.Add("Cherry");

        Console.WriteLine("Initial list:");
        foreach (string fruit in stringList)
        {
            Console.WriteLine($"- {fruit}");
        }

        // Access element by index
        Console.WriteLine($"\nElement at index 1: {stringList[1]}");

        // Insert an element
        stringList.Insert(1, "Blueberry");
        Console.WriteLine("\nList after inserting 'Blueberry' at index 1:");
        foreach (string fruit in stringList)
        {
            Console.WriteLine($"- {fruit}");
        }

        // Check if an element exists
        bool containsBanana = stringList.Contains("Banana");
        Console.WriteLine($"\nDoes the list contain 'Banana'? {containsBanana}");

        // Find the index of an element
        int cherryIndex = stringList.IndexOf("Cherry");
        Console.WriteLine($"Index of 'Cherry': {cherryIndex}");

        // Remove an element
        stringList.Remove("Banana");
        Console.WriteLine("\nList after removing 'Banana':");
        foreach (string fruit in stringList)
        {
            Console.WriteLine($"- {fruit}");
        }

        // Remove element at index
        stringList.RemoveAt(0); // Removes "Apple"
        Console.WriteLine("\nList after removing element at index 0:");
        foreach (string fruit in stringList)
        {
            Console.WriteLine($"- {fruit}");
        }

        // Clear the list
        stringList.Clear();
        Console.WriteLine($"\nList count after clearing: {stringList.Count}");
    }
}

Note: The System.Collections.Generic.List<T> class is a common implementation of the IList<T> interface.