Learn how getElementsByClassName() behaves in JavaScript: it returns an empty HTMLCollection, not undefined, when no elements match the class. Ensure robust code by checking the length property to handle empty results effectively.

In C#, Collection helps in managing the group of objects in a flexible manner to perform operations like insert, delete, etc. on the object items in a dynamic manner. Collections is having predefined classes which helps in providing different operations like sorting objects, searching objects, deleting objects and many more. The predefined classes are present under System.Collections namespace.