What is the difference between DataSet and DataReader?

Short answer: DataSet: It is a disconnected, in-memory data structure that can hold multiple tables.

Explain a bit more

It can also be updated and later written back to the database. You can move back and forth between rows (using DataRow and DataColumn). DataReader: A DataReader is a forward-only, read-only data cursor. It provides faster, streaming access to the data from the database but doesn’t allow modifications. It maintains an open connection while reading data. Example: DataSet: If you're working on a report with multiple tables, such as Customers, Orders, and Products, you'd use a DataSet. DataReader: If you're fetching customer details one by one for a quick operation, a DataReader would be used.

Real-world example (ShopNest)

For large order exports, ShopNest uses SqlDataReader (forward-only, fast). DataSet is heavier and mainly for disconnected editing scenarios.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.