What are the scenarios where C# indexers are used?

1. The indexer can be used to access and manipulate collection data in a class, similar to accessing arrays, simplifying the manipulation of collection data.
2. An indexer can be used to achieve functions similar to a dictionary, allowing for the retrieval or setting of corresponding values by specifying a key.
3. The indexer can be used to access elements in a class, simplifying the way the class is operated and used.
4. The indexer can be used to achieve functions similar to properties, allowing values to be accessed or set through an index.
5. Indexers can be used to manage data structures within a class, providing a more convenient way to access and manipulate them.

In conclusion, the main scenario for using indexers is when there is a need to access and manipulate data within a class. Indexers can help simplify code and improve readability and usability.