IDataReader

IDataReader is an interface in the .NET Framework that represents a read-only stream of data from a data source. It is a fundamental component for accessing data in a forward-only, connected manner. When you execute a query that returns multiple rows and columns, a data provider typically returns an IDataReader object.

The primary purpose of IDataReader is to provide efficient, low-level access to data. It allows you to retrieve data row by row without loading the entire result set into memory. This is particularly beneficial for large datasets where memory consumption can be a concern.

Key methods of the IDataReader interface include Read(), which advances the reader to the next record, and GetValue(int ordinal), which retrieves the value of the column at the specified ordinal position. It also provides methods like GetInt32, GetString, and GetDateTime for retrieving column values as specific data types.

IDataReader is designed for a single, forward-only pass through the data. You cannot move backward or jump to arbitrary records. Once a record is read, it cannot be revisited. This design contributes to its performance and efficiency.

Commonly, IDataReader is used in conjunction with commands executed against databases. For instance, a SqlCommand object in ADO.NET can return an object that implements IDataReader, allowing you to iterate through the query results. Implementations of IDataReader are provided by various data providers, such as SqlDataReader for SQL Server, OracleDataReader for Oracle, and OdbcDataReader for ODBC data sources.