Class NpgsqlDataReader

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

Inheritance
Object
MarshalByRefObject
DbDataReader
NpgsqlDataReader
Implements
Inherited Members
Namespace: Npgsql
Assembly: Npgsql.dll
Syntax
public sealed class NpgsqlDataReader : DbDataReader, IEnumerable, IDataReader, IDataRecord, IDisposable, IAsyncDisposable, IDbColumnSchemaGenerator

Properties

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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
Int32
Overrides
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FieldCount

Gets the number of columns in the current row.

Declaration
public override int FieldCount { get; }
Property Value
Type Description
Int32
Overrides
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HasRows

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

Declaration
public override bool HasRows { get; }
Property Value
Type Description
Boolean
Overrides
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IsClosed

Gets a value indicating whether the data reader is closed.

Declaration
public override bool IsClosed { get; }
Property Value
Type Description
Boolean
Overrides
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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
Boolean
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Item[Int32]

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

Declaration
public override object this[int ordinal] { get; }
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Property Value
Type Description
Object

The value of the specified column.
Overrides
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Item[String]

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

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.
Overrides
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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
Int32

The number of rows changed, inserted, or deleted. -1 for SELECT statements; 0 if no rows were affected or the statement failed.
Overrides
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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
UInt64

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

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

Declaration
[Obsolete("Use the new DbBatch API")]
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

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Close()

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

Declaration
public override void Close()
Overrides
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CloseAsync()

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

Declaration
public override Task CloseAsync()
Returns
Type Description
Task
Overrides
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Dispose(Boolean)

Releases the resources used by the NpgsqlDataReader.

Declaration
protected override void Dispose(bool disposing)
Parameters
Type Name Description
Boolean disposing
Overrides
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DisposeAsync()

Releases the resources used by the NpgsqlDataReader.

Declaration
public override ValueTask DisposeAsync()
Returns
Type Description
ValueTask
Overrides
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GetBoolean(Int32)

Gets the value of the specified column as a Boolean.

Declaration
public override bool GetBoolean(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Boolean

The value of the specified column.
Overrides
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GetByte(Int32)

Gets the value of the specified column as a byte.

Declaration
public override byte GetByte(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Byte

The value of the specified column.
Overrides
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GetBytes(Int32, Int64, Byte[], Int32, Int32)

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
Int32 ordinal

The zero-based column ordinal.
Int64 dataOffset

The index within the row from which to begin the read operation.
Byte[] buffer

The buffer into which to copy the data.
Int32 bufferOffset

The index with the buffer to which the data will be copied.
Int32 length

The maximum number of characters to read.
Returns
Type Description
Int64

The actual number of bytes read.
Overrides
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GetChar(Int32)

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

Declaration
public override char GetChar(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Char

The value of the specified column.
Overrides
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GetChars(Int32, Int64, Char[], Int32, Int32)

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
Int32 ordinal

The zero-based column ordinal.
Int64 dataOffset

The index within the row from which to begin the read operation.
Char[] buffer

The buffer into which to copy the data.
Int32 bufferOffset

The index with the buffer to which the data will be copied.
Int32 length

The maximum number of characters to read.
Returns
Type Description
Int64

The actual number of characters read.
Overrides
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GetColumnSchema()

Returns schema information for the columns in the current resultset.

Declaration
public ReadOnlyCollection<NpgsqlDbColumn> GetColumnSchema()
Returns
Type Description
ReadOnlyCollection<NpgsqlDbColumn>
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GetColumnSchemaAsync(CancellationToken)

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

Declaration
public Task<ReadOnlyCollection<NpgsqlDbColumn>> GetColumnSchemaAsync(CancellationToken cancellationToken = default(CancellationToken))
Parameters
Type Name Description
CancellationToken cancellationToken
Returns
Type Description
Task<ReadOnlyCollection<NpgsqlDbColumn>>
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GetData(Int32)

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
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
NpgsqlNestedDataReader

A data reader.
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GetDataTypeName(Int32)

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(Int32) for that).

Declaration
public override string GetDataTypeName(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column index.
Returns
Type Description
String
Overrides
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GetDataTypeOID(Int32)

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
Int32 ordinal

The zero-based column index.
Returns
Type Description
UInt32
Remarks

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

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GetDateTime(Int32)

Gets the value of the specified column as a DateTime object.

Declaration
public override DateTime GetDateTime(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
DateTime

The value of the specified column.
Overrides
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GetDbDataReader(Int32)

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

Declaration
protected override DbDataReader GetDbDataReader(int ordinal)
Parameters
Type Name Description
Int32 ordinal
Returns
Type Description
DbDataReader
Overrides
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GetDecimal(Int32)

Gets the value of the specified column as a Decimal object.

Declaration
public override decimal GetDecimal(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Decimal

The value of the specified column.
Overrides
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GetDouble(Int32)

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
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Double

The value of the specified column.
Overrides
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GetEnumerator()

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

Declaration
public override IEnumerator GetEnumerator()
Returns
Type Description
IEnumerator

An IEnumerator that can be used to iterate through the rows in the data reader.
Overrides
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GetFieldType(Int32)

Gets the data type of the specified column.

Declaration
public override Type GetFieldType(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Type

The data type of the specified column.
Overrides
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GetFieldValue<T>(Int32)

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

Declaration
public override T GetFieldValue<T>(int ordinal)
Parameters
Type Name Description
Int32 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.
Overrides
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GetFieldValueAsync<T>(Int32, 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
Int32 ordinal

The type of the value to be returned.
CancellationToken cancellationToken

An optional token to cancel the asynchronous operation. The default value is None.
Returns
Type Description
Task<T>
Type Parameters
Name Description
T

The type of the value to be returned.
Overrides
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GetFloat(Int32)

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
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Single

The value of the specified column.
Overrides
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GetGuid(Int32)

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

Declaration
public override Guid GetGuid(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Guid

The value of the specified column.
Overrides
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GetInt16(Int32)

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

Declaration
public override short GetInt16(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Int16

The value of the specified column.
Overrides
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GetInt32(Int32)

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

Declaration
public override int GetInt32(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Int32

The value of the specified column.
Overrides
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GetInt64(Int32)

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

Declaration
public override long GetInt64(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Int64

The value of the specified column.
Overrides
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GetName(Int32)

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

Declaration
public override string GetName(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
String

The name of the specified column.
Overrides
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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
Int32

The zero-based column ordinal.
Overrides
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GetPostgresType(Int32)

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
Int32 ordinal

The zero-based column index.
Returns
Type Description
PostgresType
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GetProviderSpecificFieldType(Int32)

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

Declaration
public override Type GetProviderSpecificFieldType(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Type

The Type object that describes the data type of the specified column.
Overrides
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GetProviderSpecificValue(Int32)

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

Declaration
public override object GetProviderSpecificValue(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Object

The value of the specified column.
Overrides
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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
Int32

The number of instances of Object in the array.
Overrides
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GetSchemaTable()

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

Declaration
public override DataTable GetSchemaTable()
Returns
Type Description
DataTable
Overrides
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GetSchemaTableAsync(CancellationToken)

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

Declaration
public Task<DataTable> GetSchemaTableAsync(CancellationToken cancellationToken = default(CancellationToken))
Parameters
Type Name Description
CancellationToken cancellationToken
Returns
Type Description
Task<DataTable>
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GetStream(Int32)

Retrieves data as a Stream.

Declaration
public override Stream GetStream(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Stream

The returned object.
Overrides
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GetStreamAsync(Int32, CancellationToken)

Retrieves data as a Stream.

Declaration
public Task<Stream> GetStreamAsync(int ordinal, CancellationToken cancellationToken = default(CancellationToken))
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
CancellationToken cancellationToken

An optional token to cancel the asynchronous operation. The default value is None.
Returns
Type Description
Task<Stream>

The returned object.
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GetString(Int32)

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

Declaration
public override string GetString(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
String

The value of the specified column.
Overrides
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GetTextReader(Int32)

Retrieves data as a TextReader.

Declaration
public override TextReader GetTextReader(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
TextReader

The returned object.
Overrides
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GetTextReaderAsync(Int32, CancellationToken)

Retrieves data as a TextReader.

Declaration
public Task<TextReader> GetTextReaderAsync(int ordinal, CancellationToken cancellationToken = default(CancellationToken))
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
CancellationToken cancellationToken

An optional token to cancel the asynchronous operation. The default value is None.
Returns
Type Description
Task<TextReader>

The returned object.
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GetTimeSpan(Int32)

Gets the value of the specified column as a TimeSpan,

Declaration
public TimeSpan GetTimeSpan(int ordinal)
Parameters
Type Name Description
Int32 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

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GetValue(Int32)

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

Declaration
public override object GetValue(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Object

The value of the specified column.
Overrides
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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
Int32

The number of instances of Object in the array.
Overrides
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IsDBNull(Int32)

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

Declaration
public override bool IsDBNull(int ordinal)
Parameters
Type Name Description
Int32 ordinal

The zero-based column ordinal.
Returns
Type Description
Boolean

true if the specified column is equivalent to DBNull; otherwise false.
Overrides
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IsDBNullAsync(Int32, CancellationToken)

An asynchronous version of IsDBNull(Int32), 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
Int32 ordinal

The zero-based column to be retrieved.
CancellationToken cancellationToken

An optional token to cancel the asynchronous operation. The default value is None.
Returns
Type Description
Task<Boolean>

true if the specified column value is equivalent to DBNull otherwise false.
Overrides
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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
Boolean
Overrides
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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 None.
Returns
Type Description
Task<Boolean>

A task representing the asynchronous operation.
Overrides
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Read()

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

Declaration
public override bool Read()
Returns
Type Description
Boolean

true if there are more rows; otherwise false.
Overrides
Remarks

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

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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 None.
Returns
Type Description
Task<Boolean>

A task representing the asynchronous operation.
Overrides

Events

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ReaderClosed

Is raised whenever Close() is called.

Declaration
public event EventHandler ReaderClosed
Event Type
Type Description
EventHandler

Explicit Interface Implementations

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IDbColumnSchemaGenerator.GetColumnSchema()

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

Declaration
ReadOnlyCollection<DbColumn> IDbColumnSchemaGenerator.GetColumnSchema()
Returns
Type Description
ReadOnlyCollection<DbColumn>

Implements