Essential ADO.NET

3.9. Reading Column Values through IDataRecord

Individual column values are read through a DataReader's implementation of the IDataRecord interface. IDataRecord includes a series of strongly typed accessors (shown in Listing 3-18) that take a zero-based column ordinal and return a CLS type. These methods map data source data types to CLS data types. Providers can choose to expose accessors for data source-specific data types; for example, the SqlClient provider's accessors can return instances of structures defined in the System.Data.SqlTypes namespace. Strongly typed accessors do not necessarily convert types; using the wrong getter (for example, calling GetString on an integer column) results in an InvalidCastException. A special method,