Class NpgsqlDataReader

Reads a forward-only stream of rows from a data source.

Inheritance

object

NpgsqlDataReader

Implements

IDbColumnSchemaGenerator

Namespace: Npgsql

Assembly: Npgsql.dll

Syntax

public sealed class NpgsqlDataReader : DbDataReader, IDbColumnSchemaGenerator

Properties

Depth

Gets a value indicating the depth of nesting for the current row. Always returns zero.

Declaration

public override int Depth { get; }

Property Value

Type	Description
int

FieldCount

Gets the number of columns in the current row.

Declaration

public override int FieldCount { get; }

Property Value

Type	Description
int

HasRows

Gets a value that indicates whether this DbDataReader contains one or more rows.

Declaration

public override bool HasRows { get; }

Property Value

Type	Description
bool

IsClosed

Gets a value indicating whether the data reader is closed.

Declaration

public override bool IsClosed { get; }

Property Value

Type	Description
bool

IsOnRow

Indicates whether the reader is currently positioned on a row, i.e. whether reading a column is possible. This property is different from HasRows in that HasRows will return true even if attempting to read a column will fail, e.g. before Read() has been called

Declaration

public bool IsOnRow { get; }

Property Value

Type	Description
bool

this[int]

Gets the value of the specified column as an instance of .

Declaration

public override object this[int ordinal] { get; }

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Property Value

Type	Description
object	The value of the specified column.

this[string]

Gets the value of the specified column as an instance of .

Declaration

public override object this[string name] { get; }

Parameters

Type	Name	Description
string	name	The name of the column.

Property Value

Type	Description
object	The value of the specified column.

RecordsAffected

Gets the number of rows changed, inserted, or deleted by execution of the SQL statement.

Declaration

public override int RecordsAffected { get; }

Property Value

Type	Description
int	The number of rows changed, inserted, or deleted. -1 for SELECT statements; 0 if no rows were affected or the statement failed.

Rows

Gets the number of rows changed, inserted, or deleted by execution of the SQL statement.

Declaration

public ulong Rows { get; }

Property Value

Type	Description
ulong	The number of rows changed, inserted, or deleted. 0 for SELECT statements, if no rows were affected or the statement failed.

Statements

Returns details about each statement that this reader will or has executed.

Declaration

public IReadOnlyList<NpgsqlBatchCommand> Statements { get; }

Property Value

Type	Description
IReadOnlyList<><NpgsqlBatchCommand>

Remarks

Note that some fields (i.e. rows and oid) are only populated as the reader traverses the result.

For commands with multiple queries, this exposes the number of rows affected on a statement-by-statement basis, unlike RecordsAffected which exposes an aggregation across all statements.

Methods

Close()

Closes the NpgsqlDataReader reader, allowing a new command to be executed.

Declaration

public override void Close()

CloseAsync()

Closes the NpgsqlDataReader reader, allowing a new command to be executed.

Declaration

public override Task CloseAsync()

Returns

Type	Description
Task

Dispose(bool)

Releases the resources used by the NpgsqlDataReader.

Declaration

protected override void Dispose(bool disposing)

Parameters

Type	Name	Description
bool	disposing

DisposeAsync()

Releases the resources used by the NpgsqlDataReader.

Declaration

public override ValueTask DisposeAsync()

Returns

Type	Description
ValueTask

GetBoolean(int)

Gets the value of the specified column as a Boolean.

Declaration

public override bool GetBoolean(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
bool	The value of the specified column.

GetByte(int)

Gets the value of the specified column as a byte.

Declaration

public override byte GetByte(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
byte	The value of the specified column.

GetBytes(int, long, byte[]?, int, int)

Reads a stream of bytes from the specified column, starting at location indicated by dataOffset, into the buffer, starting at the location indicated by bufferOffset.

Declaration

public override long GetBytes(int ordinal, long dataOffset, byte[]? buffer, int bufferOffset, int length)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.
long	dataOffset	The index within the row from which to begin the read operation.
byte[]	buffer	The buffer into which to copy the data.
int	bufferOffset	The index with the buffer to which the data will be copied.
int	length	The maximum number of characters to read.

Returns

Type	Description
long	The actual number of bytes read.

GetChar(int)

Gets the value of the specified column as a single character.

Declaration

public override char GetChar(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
char	The value of the specified column.

GetChars(int, long, char[]?, int, int)

Reads a stream of characters from the specified column, starting at location indicated by dataOffset, into the buffer, starting at the location indicated by bufferOffset.

Declaration

public override long GetChars(int ordinal, long dataOffset, char[]? buffer, int bufferOffset, int length)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.
long	dataOffset	The index within the row from which to begin the read operation.
char[]	buffer	The buffer into which to copy the data.
int	bufferOffset	The index with the buffer to which the data will be copied.
int	length	The maximum number of characters to read.

Returns

Type	Description
long	The actual number of characters read.

GetColumnSchema()

Returns schema information for the columns in the current resultset.

Declaration

public ReadOnlyCollection<NpgsqlDbColumn> GetColumnSchema()

Returns

Type	Description
ReadOnlyCollection<><NpgsqlDbColumn>

GetColumnSchemaAsync(CancellationToken)

Asynchronously returns schema information for the columns in the current resultset.

Declaration

public Task<ReadOnlyCollection<NpgsqlDbColumn>> GetColumnSchemaAsync(CancellationToken cancellationToken = null)

Parameters

Type	Name	Description
CancellationToken	cancellationToken

Returns

Type	Description
Task<><ReadOnlyCollection<><NpgsqlDbColumn>>

GetData(int)

Returns a nested data reader for the requested column. The column type must be a record or a to Npgsql known composite type, or an array thereof. Currently only supported in non-sequential mode.

Declaration

public NpgsqlNestedDataReader GetData(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
NpgsqlNestedDataReader	A data reader.

GetDataTypeName(int)

Gets the data type information for the specified field. This is the PostgreSQL type name (e.g. double precision), not the .NET type (see GetFieldType(int) for that).

Declaration

public override string GetDataTypeName(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column index.

Returns

Type	Description
string

GetDataTypeOID(int)

Gets the OID for the PostgreSQL type for the specified field, as it appears in the pg_type table.

Declaration

public uint GetDataTypeOID(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column index.

Returns

Type	Description
uint

Remarks

This is a PostgreSQL-internal value that should not be relied upon and should only be used for debugging purposes.

GetDateTime(int)

Gets the value of the specified column as a object.

Declaration

public override DateTime GetDateTime(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
DateTime	The value of the specified column.

GetDbDataReader(int)

Declaration

protected override DbDataReader GetDbDataReader(int ordinal)

Parameters

Type	Name	Description
int	ordinal

Returns

Type	Description
DbDataReader

GetDecimal(int)

Gets the value of the specified column as a object.

Declaration

public override decimal GetDecimal(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
decimal	The value of the specified column.

GetDouble(int)

Gets the value of the specified column as a double-precision floating point number.

Declaration

public override double GetDouble(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
double	The value of the specified column.

GetEnumerator()

Returns an that can be used to iterate through the rows in the data reader.

Declaration

public override IEnumerator GetEnumerator()

Returns

Type	Description
IEnumerator	An that can be used to iterate through the rows in the data reader.

GetFieldType(int)

Gets the data type of the specified column.

Declaration

public override Type GetFieldType(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
Type	The data type of the specified column.

GetFieldValue<T>(int)

Synchronously gets the value of the specified column as a type.

Declaration

public override T GetFieldValue<T>(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The column to be retrieved.

Returns

Type	Description
T	The column to be retrieved.

Type Parameters

Name	Description
T	Synchronously gets the value of the specified column as a type.

GetFieldValueAsync<T>(int, CancellationToken)

Asynchronously gets the value of the specified column as a type.

Declaration

public override Task<T> GetFieldValueAsync<T>(int ordinal, CancellationToken cancellationToken)

Parameters

Type	Name	Description
int	ordinal	The type of the value to be returned.
CancellationToken	cancellationToken	An optional token to cancel the asynchronous operation. The default value is .

Returns

Type	Description
Task<><T>

Type Parameters

Name	Description
T	The type of the value to be returned.

GetFloat(int)

Gets the value of the specified column as a single-precision floating point number.

Declaration

public override float GetFloat(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
float	The value of the specified column.

GetGuid(int)

Gets the value of the specified column as a globally-unique identifier (GUID).

Declaration

public override Guid GetGuid(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
Guid	The value of the specified column.

GetInt16(int)

Gets the value of the specified column as a 16-bit signed integer.

Declaration

public override short GetInt16(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
short	The value of the specified column.

GetInt32(int)

Gets the value of the specified column as a 32-bit signed integer.

Declaration

public override int GetInt32(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
int	The value of the specified column.

GetInt64(int)

Gets the value of the specified column as a 64-bit signed integer.

Declaration

public override long GetInt64(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
long	The value of the specified column.

GetName(int)

Gets the name of the column, given the zero-based column ordinal.

Declaration

public override string GetName(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
string	The name of the specified column.

GetOrdinal(string)

Gets the column ordinal given the name of the column.

Declaration

public override int GetOrdinal(string name)

Parameters

Type	Name	Description
string	name	The name of the column.

Returns

Type	Description
int	The zero-based column ordinal.

GetPostgresType(int)

Gets a representation of the PostgreSQL data type for the specified field. The returned representation can be used to access various information about the field.

Declaration

public PostgresType GetPostgresType(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column index.

Returns

Type	Description
PostgresType

GetProviderSpecificFieldType(int)

Returns the provider-specific field type of the specified column.

Declaration

public override Type GetProviderSpecificFieldType(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
Type	The Type object that describes the data type of the specified column.

GetProviderSpecificValue(int)

Gets the value of the specified column as an instance of .

Declaration

public override object GetProviderSpecificValue(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
object	The value of the specified column.

GetProviderSpecificValues(object[])

Gets all provider-specific attribute columns in the collection for the current row.

Declaration

public override int GetProviderSpecificValues(object[] values)

Parameters

Type	Name	Description
object[]	values	An array of Object into which to copy the attribute columns.

Returns

Type	Description
int	The number of instances of in the array.

GetSchemaTable()

Returns a System.Data.DataTable that describes the column metadata of the DataReader.

Declaration

public override DataTable? GetSchemaTable()

Returns

Type	Description
DataTable?

GetSchemaTableAsync(CancellationToken)

Asynchronously returns a System.Data.DataTable that describes the column metadata of the DataReader.

Declaration

public Task<DataTable?> GetSchemaTableAsync(CancellationToken cancellationToken = null)

Parameters

Type	Name	Description
CancellationToken	cancellationToken

Returns

Type	Description
Task<><DataTable?>

GetStream(int)

Retrieves data as a .

Declaration

public override Stream GetStream(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
Stream	The returned object.

GetStreamAsync(int, CancellationToken)

Retrieves data as a .

Declaration

public Task<Stream> GetStreamAsync(int ordinal, CancellationToken cancellationToken = null)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.
CancellationToken	cancellationToken	An optional token to cancel the asynchronous operation. The default value is .

Returns

Type	Description
Task<><Stream>	The returned object.

GetString(int)

Gets the value of the specified column as an instance of .

Declaration

public override string GetString(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
string	The value of the specified column.

GetTextReader(int)

Retrieves data as a .

Declaration

public override TextReader GetTextReader(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
TextReader	The returned object.

GetTextReaderAsync(int, CancellationToken)

Retrieves data as a .

Declaration

public Task<TextReader> GetTextReaderAsync(int ordinal, CancellationToken cancellationToken = null)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.
CancellationToken	cancellationToken	An optional token to cancel the asynchronous operation. The default value is .

Returns

Type	Description
Task<><TextReader>	The returned object.

GetTimeSpan(int)

Gets the value of the specified column as a TimeSpan,

Declaration

public TimeSpan GetTimeSpan(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
TimeSpan	The value of the specified column.

Remarks

PostgreSQL's interval type has has a resolution of 1 microsecond and ranges from -178000000 to 178000000 years, while .NET's TimeSpan has a resolution of 100 nanoseconds and ranges from roughly -29247 to 29247 years. See https://www.postgresql.org/docs/current/static/datatype-datetime.html

GetValue(int)

Gets the value of the specified column as an instance of .

Declaration

public override object GetValue(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
object	The value of the specified column.

GetValues(object[])

Populates an array of objects with the column values of the current row.

Declaration

public override int GetValues(object[] values)

Parameters

Type	Name	Description
object[]	values	An array of Object into which to copy the attribute columns.

Returns

Type	Description
int	The number of instances of in the array.

IsDBNull(int)

Gets a value that indicates whether the column contains nonexistent or missing values.

Declaration

public override bool IsDBNull(int ordinal)

Parameters

Type	Name	Description
int	ordinal	The zero-based column ordinal.

Returns

Type	Description
bool	true if the specified column is equivalent to ; otherwise false.

IsDBNullAsync(int, CancellationToken)

An asynchronous version of IsDBNull(int), which gets a value that indicates whether the column contains non-existent or missing values. The cancellationToken parameter is currently ignored.

Declaration

public override Task<bool> IsDBNullAsync(int ordinal, CancellationToken cancellationToken)

Parameters

Type	Name	Description
int	ordinal	The zero-based column to be retrieved.
CancellationToken	cancellationToken	An optional token to cancel the asynchronous operation. The default value is .

Returns

Type	Description
Task<><bool>	true if the specified column value is equivalent to otherwise false.

NextResult()

Advances the reader to the next result when reading the results of a batch of statements.

Declaration

public override bool NextResult()

Returns

Type	Description
bool

NextResultAsync(CancellationToken)

This is the asynchronous version of NextResult.

Declaration

public override Task<bool> NextResultAsync(CancellationToken cancellationToken)

Parameters

Type	Name	Description
CancellationToken	cancellationToken	An optional token to cancel the asynchronous operation. The default value is .

Returns

Type	Description
Task<><bool>	A task representing the asynchronous operation.

Read()

Advances the reader to the next record in a result set.

Declaration

public override bool Read()

Returns

Type	Description
bool	true if there are more rows; otherwise false.

Remarks

The default position of a data reader is before the first record. Therefore, you must call Read to begin accessing data.

ReadAsync(CancellationToken)

This is the asynchronous version of Read()

Declaration

public override Task<bool> ReadAsync(CancellationToken cancellationToken)

Parameters

Type	Name	Description
CancellationToken	cancellationToken	An optional token to cancel the asynchronous operation. The default value is .

Returns

Type	Description
Task<><bool>	A task representing the asynchronous operation.

Events

ReaderClosed

Is raised whenever Close() is called.

Declaration

public event EventHandler? ReaderClosed

Event Type

Type	Description
EventHandler?

Implements

IDbColumnSchemaGenerator