A.2 The OLE DB Provider

The OLE DB provider interface provides access to a database through an OLE DB provider installed on your computer. Most OLE DB providers are supported, but those that use OLE DB Version 2.5 interfaces aren't supported. Some unsupported OLE DB interfaces include:

• OLE DB provider for ODBC (MSDASQL)

• OLE DB provider for Exchange (ExOLEDB)

• OLE DB for Internet Publishing (MSDAIPP)

Table A-3 lists some commonly used OLE DB drivers.

Table A-3. Commonly used OLE DB drivers

Name	Description
SQLOLEDB	OLE DB provider for SQL Server
MSDAORA	OLE DB provider for Oracle 7.3 and Oracle 8.
Microsoft.Jet.OLEDB.4.0	OLE DB provider for Access (and other Jet data sources)

All OLE DB types are contained in the System.Data.OleDb namespace (see Table A-4). For low-level information about OLE DB providers, you can refer to the OLE DB programmer's reference on MSDN at http://msdn.microsoft.com/library/en-us/oledb/htm/oledb_providers_overview.asp.

Table A-4. OLE DB .NET provider classes

Interface	Implementing class
IDbConnection	OleDbConnection
IDbCommand	OleDbCommand
IDataParameter , IDbDataParameter	OleDbParameter
IDataReader , IDataRecord	OleDbDataReader
IDataAdapter , IDbDataAdapter	OleDbDataAdapter
IDbTransaction	OleDbTransaction

The OLE DB managed provider doesn't include any structures for OLE DB types. However, the OleDbDataReader does include additional methods that allow you to specify the data type when retrieving a column value. Table A-5 shows the mapping between OLE DB types and .NET framework types (although it doesn't include types used exclusively for stored procedure parameters).

Table A-5. OLE DB type mappings

OLE DB data type	Mapped .NET type	Name in OleDBType enumeration
DBTYPE_I8	Int64	BigInt
DBTYPE_BYTES	Byte[]	Binary
DBTYPE_BOOL	Boolean	Boolean
DBTYPE_BSTR	String	BSTR
DBTYPE_STR	String	Char
DBTYPE_CY	Decimal	Currency
DBTYPE_DATE	DateTime	Date
DBTYPE_DBDATE	DateTime	DBDate
DBTYPE_DBTIME	TimeSpan	DBTime
DBTYPE_DBTIMESTAMP	DateTime	DBTimeStamp
DBTYPE_DECIMAL	Decimal	Decimal
DBTYPE_R8	Double	Double
DBTYPE_EMPTY	Not applicable	Empty
DBTYPE_ERROR	Exception	Error
DBTYPE_FILETIME	DateTime	Filetime
DBTYPE_GUID	Guid	Guid
DBTYPE_IDISPATCH	Not supported	IDispatch
DBTYPE_I4	Int32	Integer
DBTYPE_UNKNOWN	Not supported	IUnknown
DBTYPE_NUMERIC	Decimal	Numeric
DBTYPE_PROPVARIANT	Object	PropVarian
DBTYPE_R4	Single	Single
DBTYPE_I2	Int16	SmallInt
DBTYPE_I1	SByte	TinyInt
DBTYPE_UI8	UInt64	UnsignedBitInt
DBTYPE_UI4	UInt32	UnsignedInt
DBTYPE_UI2	UInt16	UnsignedSmallInt
DBTYPE_UI1	Byte	UnsignedTinyInt
DBTYPE_VARIANT	Object	Variant
DBTYPE_WSTR	String	WChar