In C# IList interface is an interface that belongs to the collection module where we can access each element by index. Or we can say that it is a collection of objects that are used to access each element individually with the help of an index. It is of both generic and non-generic types. Its implementation is generally categorized into three parts that are:

• read-only: In which the IList cannot be modified.
• fixed-size: In which IList is not allowed to add or remove elements.
• variable size: In which IList is allowed to modify, add, or remove elements.

Syntax:

// For Non_generic IList
public interface IList : System.Collections.ICollection

// For Generic IList
public interface IList<T> : System.Collections.Generic.ICollection<T>,
                            System.Collections.Generic.IEnumerable<T>

Properties:

Some of the commonly used properties of the IList interface are:

Methods: 

Some of the commonly used methods of the IList interface are:

Now we understand the working of IList interface with the help of an example. In the below example, we create a list with subjects and students and display the list. So to do this we have to follow the following approach:

Approach:

1. Create an array of subjects

{"os","cn","php","c/cpp","java/jsp","python/r"}

2. Create a list of student names and add names into it using Add() method.

List<string> data = new List<string>();
data.Add("sai");
data.Add("sravan");
data.Add("jyothika");

3. Define an IList Interface to display the students and subjects names.

 static void Show(IList<string> list)
{
    // Iterate through list
    foreach (string str in list)
    {
        // Print
        Console.WriteLine("\t" + str);
    }
 }

4. Call the Show() method to display the list of students and subjects.

Show(subjects);
Show(data);

Example:

Output:

Subjects Name: 
    OS
    CN
    PHP
    C/CPP
    Java/Jsp
    Python/R
Students Name: 
    sai
    sravan
    jyothika