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Mapping Data Provider Data Types to .NET Framework Data Types 

The ADO.NET DataSet object is independent of any specific data source. Data in a DataSet is retrieved from a data source, and changes are persisted back to the data source using a DataAdapter. This means that when a DataAdapter fills a DataTable in a DataSet with values from a data source, the resulting data types of the columns in the DataTable are .NET Framework types, rather than types specific to the .NET Framework data provider used to connect to the data source.

Likewise, when a DataReader returns a value from a data source, the resulting value is stored in a local variable that has a .NET Framework type.

For both the Fill operations of the DataAdapter and the Get methods of the DataReader, the .NET Framework type is inferred from the type returned from the .NET Framework data provider. We recommend that you use the typed accessor methods of the DataReader when you know the specific type of the value being returned. Typed accessor methods result in better performance by returning a value as a specific .NET Framework type, eliminating the need for additional type conversion. The SqlDataReader exposes SQL Server–specific typed accessor methods if a .NET Framework type does not meet the needs of the application. SQL Server–specific typed accessor methods return objects of System.Data.SqlTypes.

NoteNote

Enhanced type support has been added in ADO.NET 2.0 for System.Data.SqlTypes. For more information, see Working with SqlTypes.

The following tables show the inferred .NET Framework type for data types from Microsoft SQL Server, OLE DB, and ODBC. The typed accessor methods for the DataReader are also listed.

NoteNote

Null values for any .NET Framework data provider data types are represented by DBNull.Value.

.NET Framework Data Provider for SQL Server

SQL Server type .NET Framework type .NET Framework typed accessor SqlType typed accessor

bigint

Int64

GetInt64()

GetSqlInt64()

binary

Byte[]

GetBytes()

GetSqlBinary()

bit

Boolean

GetBoolean()

GetSqlBoolean()

char

String

Char[]

GetString()

GetChars()

GetSqlString()

datetime

DateTime

GetDateTime()

GetSqlDateTime()

decimal

Decimal

GetDecimal()

GetSqlDecimal()

float

Double

GetDouble()

GetSqlDouble()

image

Byte[]

GetBytes()

GetSqlBinary()

int

Int32

GetInt32()

GetSqlInt32()

money

Decimal

GetDecimal()

GetSqlMoney()

nchar

String

Char[]

GetString()

GetChars()

GetSqlString()

ntext

String

Char[]

GetString()

GetChars()

GetSqlString()

numeric

Decimal

GetDecimal()

GetSqlDecimal()

nvarchar

String

Char[]

GetString()

GetChars()

GetSqlString()

real

Single

GetFloat()

GetSqlSingle()

smalldatetime

DateTime

GetDateTime()

GetSqlDateTime()

smallint

Int16

GetInt16()

GetSqlInt16()

smallmoney

Decimal

GetDecimal()

GetSqlDecimal()

sql_variant

Object *

GetValue() *

GetSqlValue() *

text

String

Char[]

GetString()

GetChars()

GetSqlString()

timestamp

Byte[]

GetBytes()

GetSqlBinary()

tinyint

Byte

GetByte()

GetSqlByte()

uniqueidentifier

Guid

GetGuid()

GetSqlGuid()

varbinary

Byte[]

GetBytes()

GetSqlBinary()

varchar

String

Char[]

GetString()

GetChars()

GetSqlString()

xml

Xml

GetXml

GetSqlXml()

* We recommend that you use a specific typed accessor if you know the underlying type of the sql_variant.

.NET Framework Data Provider for OLE DB

ADO type OLE DB type .NET Framework type .NET Framework typed accessor

adBigInt

DBTYPE_I8

Int64

GetInt64()

adBinary

DBTYPE_BYTES

Byte[]

GetBytes()

adBoolean

DBTYPE_BOOL

Boolean

GetBoolean()

adBSTR

DBTYPE_BSTR

String

GetString()

adChapter

DBTYPE_HCHAPTER

Supported through the DataReader. See Retrieving Data Using a DataReader.

GetValue()

adChar

DBTYPE_STR

String

GetString()

adCurrency

DBTYPE_CY

Decimal

GetDecimal()

adDate

DBTYPE_DATE

DateTime

GetDateTime()

adDBDate

DBTYPE_DBDATE

DateTime

GetDateTime()

adDBTime

DBTYPE_DBTIME

DateTime

GetDateTime()

adDBTimeStamp

DBTYPE_DBTIMESTAMP

DateTime

GetDateTime()

adDecimal

DBTYPE_DECIMAL

Decimal

GetDecimal()

adDouble

DBTYPE_R8

Double

GetDouble()

adError

DBTYPE_ERROR

ExternalException

GetValue()

adFileTime

DBTYPE_FILETIME

DateTime

GetDateTime()

adGUID

DBTYPE_GUID

Guid

GetGuid()

adIDispatch

DBTYPE_IDISPATCH *

Object

GetValue()

adInteger

DBTYPE_I4

Int32

GetInt32()

adIUnknown

DBTYPE_IUNKNOWN *

Object

GetValue()

adNumeric

DBTYPE_NUMERIC

Decimal

GetDecimal()

adPropVariant

DBTYPE_PROPVARIANT

Object

GetValue()

adSingle

DBTYPE_R4

Single

GetFloat()

adSmallInt

DBTYPE_I2

Int16

GetInt16()

adTinyInt

DBTYPE_I1

Byte

GetByte()

adUnsignedBigInt

DBTYPE_UI8

UInt64

GetValue()

adUnsignedInt

DBTYPE_UI4

UInt32

GetValue()

adUnsignedSmallInt

DBTYPE_UI2

UInt16

GetValue()

adUnsignedTinyInt

DBTYPE_UI1

Byte

GetByte()

adVariant

DBTYPE_VARIANT

Object

GetValue()

adWChar

DBTYPE_WSTR

String

GetString()

adUserDefined

DBTYPE_UDT

not supported

   

adVarNumeric

DBTYPE_VARNUMERIC

not supported

   

  • * For OLE DB types DBTYPE_IUNKNOWN and DBTYPE_IDISPATCH, the object reference is a marshaled representation of the pointer.

.NET Framework Data Provider for ODBC

ODBC type .NET Framework type .NET Framework typed accessor

SQL_BIGINT

Int64

GetInt64()

SQL_BINARY

Byte[]

GetBytes()

SQL_BIT

Boolean

GetBoolean()

SQL_CHAR

String

Char[]

GetString()

GetChars()

SQL_DECIMAL

Decimal

GetDecimal()

SQL_DOUBLE

Double

GetDouble()

SQL_GUID

Guid

GetGuid()

SQL_INTEGER

Int32

GetInt32()

SQL_LONG_VARCHAR

String

Char[]

GetString()

GetChars()

SQL_LONGVARBINARY

Byte[]

GetBytes()

SQL_NUMERIC

Decimal

GetDecimal()

SQL_REAL

Single

GetFloat()

SQL_SMALLINT

Int16

GetInt16()

SQL_TINYINT

Byte

GetByte()

SQL_TYPE_TIMES

DateTime

GetDateTime()

SQL_TYPE_TIMESTAMP

DateTime

GetDateTime()

SQL_VARBINARY

Byte[]

GetBytes()

SQL_WCHAR

String

Char[]

GetString()

GetChars()

SQL_WLONGVARCHAR

String

Char[]

GetString()

GetChars()

SQL_WVARCHAR

String

Char[]

GetString()

GetChars()

.NET Framework Data Provider for Oracle

Oracle type .NET Framework type .NET Framework typed accessor OracleType typed accessor

BFILE

Byte[]

GetBytes()

GetOracleBFile()

BLOB

Byte[]

GetBytes()

GetOracleLob()

CHAR

String

Char[]

GetString()

GetChars()

GetOracleString()

CLOB

String

Char[]

GetString()

GetChars()

GetOracleLob()

DATE

DateTime

GetDateTime()

GetOracleDateTime()

FLOAT

Decimal

GetDecimal()

GetOracleNumber() **

INTEGER

Decimal

GetDecimal()

GetOracleNumber() **

INTERVAL YEAR TO MONTH *

Int32

GetInt32()

GetOracleMonthSpan()

INTERVAL DAY TO SECOND *

TimeSpan

GetTimeSpan()

GetOracleTimeSpan()

LONG

String

Char[]

GetString()

GetChars()

GetOracleString()

LONG RAW

Byte[]

GetBytes()

GetOracleBinary()

NCHAR

String

Char[]

GetString()

GetChars()

GetOracleString()

NCLOB

String

Char[]

GetString()

GetChars()

GetOracleLob()

NUMBER

Decimal

GetDecimal()

GetOracleNumber() **

NVARCHAR2

String

Char[]

GetString()

GetChars()

GetOracleString()

RAW

Byte[]

GetBytes()

GetOracleBinary()

REF CURSOR

 

 

 

ROWID

String

Char[]

GetString()

GetChars()

GetOracleString()

TIMESTAMP *

DateTime

GetDateTime()

GetOracleDateTime()

TIMESTAMP WITH LOCAL TIME ZONE *

DateTime

GetDateTime()

GetOracleDateTime()

TIMESTAMP WITH TIME ZONE *

DateTime

GetDateTime()

GetOracleDateTime()

UNSIGNED INTEGER

Decimal

GetDecimal()

GetOracleNumber() **

VARCHAR2

String

Char[]

GetString()

GetChars()

GetOracleString()

* The specified Oracle type is only available when using both Oracle 9i client and server software.

** An Oracle NUMBER can have a maximum of 38 significant digits. The .NET Framework decimal type is limited to 28 digits. Reading an Oracle NUMBER into a .NET Framework decimal type results in an OverflowException for NUMBER values exceeding 28 digits. If you are reading an Oracle NUMBER value from an OracleDataReader, we recommend that you call the GetOracleNumber typed accessor method to return Oracle NUMBER values as an OracleNumber. If you are filling a DataSet, you can use the FillError event to determine whether an OverflowException has occurred and take appropriate action. For information on the FillError event, see Working with DataAdapter Events.

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