SQL Server and the .NET Framework are based on different type systems. For example, the .NET Framework Decimal structure has a maximum scale of 28, whereas the SQL Server decimal and numeric data types have a maximum scale of 38. To maintain data integrity when reading and writing data, theSqlDataReader exposes SQL Server–specific typed accessor methods that return objects of System.Data.SqlTypes as well as accessor methods that return .NET Framework types. Both SQL Server types and .NET Framework types are also represented by enumerations in the DbType and SqlDbTypeclasses, which you can use when specifying SqlParameter data types.
The following table shows the inferred .NET Framework type, the DbType and SqlDbType enumerations, and the accessor methods for theSqlDataReader.
* Use a specific typed accessor if you know the underlying type of the sql_variant.