Ingres 11.0 | IngresDataReader Class

Connectivity Guide > Connectivity Guide > Understanding .NET Data Provider Connectivity > .NET Data Provider Classes > IngresDataReader Class

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IngresDataReader Class

IngresDataReader provides a means of reading a forward-only stream of rows from a result-set created by a SELECT query or a row-producing database procedure.

When an IngresDataReader is open, the IngresConnection is busy and no other operations are allowed on the IngresConnection (other than IngresConnection.Close) until IngresDataReader.Close is issued. Created by the IngresCommand.ExecuteReader methods.

IngresDataReader Class Declaration

The IngresDataReader can be declared as follows:

C#: public sealed class IngresDataReader : System.Data.Common.DbDataReader

VB.NET: NotInheritable Public Class IngresDataReader
Inherits System.Data.Common.DbDataReader

IngresDataReader Class Example

The following is an example implementation of the IngresDataReader class:

static void ReaderDemo(string connstring)

{

IngresConnection conn = new IngresConnection(connstring);

string strNumber;

string strName;

string strSSN;

conn.Open();

IngresCommand cmd = new IngresCommand(

"select number, name, ssn from personnel", conn);

IngresDataReader reader = cmd.ExecuteReader();

Console.Write(reader.GetName(0) + "\t");

Console.Write(reader.GetName(1) + "\t");

Console.Write(reader.GetName(2));

Console.WriteLine();

while (reader.Read())

{

strNumber= reader.IsDBNull(0)?

"<none>":reader.GetInt32(0).ToString();

strName = reader.IsDBNull(1)?

"<none>":reader.GetString(1);

strSSN = reader.IsDBNull(2)?

"<none>":reader.GetString(2);

Console.WriteLine(

strNumber + "\t" + strName + "\t" + strSSN);

}

reader.Close();

conn.Close();

}

IngresDataReader Class Properties

The IngresDataReader class contains the following properties:

Property	Accessor	Description
Depth	get	The depth of nesting for the current row. This data provider always returns a depth of zero to indicate no nesting of tables.
FieldCount	get	The number of columns in the current row.
HasRows	get	Returns true if the data reader contains one or more rows. Returns false if the data reader contains zero rows.
IsClosed	get	A true/false indicator as to whether the data reader is closed.
Item	get	Gets the column value in its native format for a given column name or column ordinal. This property is the C# indexer for the IngresDataReader class.
RecordsAffected	get	The number of rows updated, inserted, or deleted by execution of the SQL statement. -1 is returned for SELECT statements.

IngresDataReader Class Public Methods

The public methods available to the IngresDataReader class are:

Method	Description
Close	Closes the IngresDataReader.
GetBoolean	Gets the column value as a Boolean.
GetByte	Gets the column value as an unsigned 8-bit Byte.
GetBytes	Gets the column value as a byte stream into a Byte array.
GetChar	Gets the column value as a Char.
GetChars	Gets the column value as a character stream into a Char array.
GetDataTypeName	Gets the column's data type name as known in Ingres.
GetDateTime	Gets the column value as a DateTime.
GetDecimal	Gets the column value as a Decimal.
GetDouble	Gets the column value as a double.
GetFieldType	Gets the column's .NET Type.
GetFloat	Gets the column value as a Float.
GetGuid	Gets the column value as a Guid.
GetInt16	Gets the column value as a signed 16-bit integer.
GetInt32	Gets the column value as a signed 32-bit integer.
GetInt64	Gets the column value as a signed 64-bit integer.
GetName	Gets the column's name using a specified ordinal.
GetOrdinal	Gets the column's ordinal using a specified name.
GetSchemaTable	Returns a DataTable that describes the resultset column metadata. If ExecuteReader( CommandBehavior.KeyInfo ) was called, additional information about primary key columns, unique columns, and base names is retrieved from the database catalog and included in the returned DataTable. For column information returned, see GetSchemaTable Columns Returned.
GetString	Gets the column value as a string.
GetTimeSpan	Gets the column value as a TimeSpan.
GetValue	Gets the column value in its native format.
GetValues	Gets all of the column values into an Object array.
IsDBNull	Returns true/false indicating whether the column value is null.
NextResult	Advances the data reader to the next result set if present.
Read	Advances the data reader to the next row in the result set.

IMPORTANT! There are no conversions performed by\ the GetXXX methods. If the data is not of the correct type, an InvalidCastException is thrown.

Always call IsDBNull on a column if there is any chance of it being null before attempting to call one of the GetXXX accessor to retrieve the data.

GetSchemaTable Columns Returned

The GetSchemaTable describes the column metadata of the IngresDataReader.

Note: The column information is not necessarily returned in the order shown.

Column Information	Data Type	Description
ColumnName	String	The name of the column, which reflects the renaming of the column in the command text (that is, the alias).
ColumnOrdinal	Int32	The number of the column, beginning with 1.
ColumnSize	Int32	Maximum possible length of a value in the column.
NumericPrecision	Int16	This is the maximum precision of the column if the column is a numeric data type; otherwise the value is null.
NumericScale	Int16	This is the number of decimal places in the column if the column is a numeric data type; otherwise the value is null.
DataType	Type	The .NET Framework data type of the column.
ProviderType	IngresType	The indicator of the column's data type
IsLong	Boolean	Set to true if the column contains a long varchar, long varbinary, or long nvarchar object; otherwise false.
AllowDBNull	Boolean	Set to true if the application can set the column to a null value or if the data provider cannot determine if the application can set the column to a null value. Set to false if it is known that the application is not permitted to set the column to a null. Note that a column value may be null even if the application is not permitted to set the null value.
IsReadOnly	Boolean	Set to true if it is known that the column cannot be modified; otherwise false.
IsRowVersion	Boolean	Set to true if column has a persistent row identifier that cannot be written to and serves only to identify the row. The .NET Data Provider always returns false.
IsUnique	Boolean	Set to true if no two rows in the table can have the same value in this column. Set to false if not unique or if uniqueness cannot be determined. Only set if ExecuteReader(CommandBehavior.KeyInfo) was called.
IsKey	Boolean	Set to true if this column is in the set of columns that, taken together, uniquely identify the row. Only set if ExecuteReader( CommandBehavior.KeyInfo ) was called.
IsAutoIncrement	Boolean	Set to true if the column assigns values to new rows in fixed increments. The .NET Data Provider always returns false.
BaseCatalogName	String	The name of the database catalog that contains the column. This value is null if the catalog name cannot be determined. The .NET Data Provider always returns a null value.
BaseSchemaName	String	The name of the database schema that contains the column. This value is null if the schema name cannot be determined. Only set if ExecuteReader(CommandBehavior.KeyInfo) was called.
BaseTableName	String	The name of the database table or view that contains the column. This value is null if the table name cannot be determined. Only set if ExecuteReader(CommandBehavior.KeyInfo) was called.
BaseColumnName	String	The name of the column in the database. This value is null if the column name cannot be determined. Only set if ExecuteReader( CommandBehavior.KeyInfo ) was called.

Mapping of Ingres Native Types to .NET Types

The following table maps the native Ingres database types supported by the .NET Data Provider to their corresponding .NET type. It also maps the typed accessor that a .NET application uses for an Ingres native database type to be obtained as a .NET type.

IngresType	Ingres Data Type	.NET Data Type	Accessor
Binary	byte	Byte[]	GetBytes()
Char	char	String	GetString()
DateTime	date	DateTime	GetDateTime()
Decimal	decimal	Decimal	GetDecimal()
Double	double precision (float8)	Double	GetDouble()
SmallInt	smallint	Int16	GetInt16()
TinyInt	integer1	Byte	GetByte()
Int	integer	Int32	GetInt32()
BigInt	bigint	Int64	GetInt64()
LongVarBinary	long byte	Byte[]	GetBytes()
LongVarChar	long varchar	String	GetString()
LongNVarChar	long nvarchar	String	GetString()
Nchar	nchar	String	GetString()
NvarChar	nvarchar	String	GetString()
Real	real (float4)	Single	GetString()
VarBinary	byte varying	Byte[]	GetBytes()
VarChar	varchar	String	GetString()
IntervalYearToMonth	interval year to month	String	GetString()
IntervalDayToSecond	interval day to second	Timespan	GetTimeSpan()

Last modified date: 01/30/2023