IDataReader Interface

Definition

Namespace:

System.Data

Assembly:

System.Data.Common.dll

Provides a means of reading one or more forward-only streams of result sets obtained by executing a command at a data source, and is implemented by .NET data providers that access relational databases.

public interface class IDataReader : IDisposable, System::Data::IDataRecord

public interface IDataReader : IDisposable, System.Data.IDataRecord

type IDataReader = interface
    interface IDataRecord
    interface IDisposable

Public Interface IDataReader
Implements IDataRecord, IDisposable

Derived

System.Data.Common.DbDataReader

Implements

IDataRecord IDisposable

Examples

The following example creates instances of the derived classes, SqlConnection, SqlCommand, and SqlDataReader. The example reads through the data, writing it out to the console. Finally, the example closes the SqlDataReader, then the SqlConnection.

private static void ReadOrderData(string connectionString)
{
    string queryString =
        "SELECT OrderID, CustomerID FROM dbo.Orders;";

    using (SqlConnection connection =
               new SqlConnection(connectionString))
    {
        SqlCommand command =
            new SqlCommand(queryString, connection);
        connection.Open();

        SqlDataReader reader = command.ExecuteReader();

        // Call Read before accessing data.
        while (reader.Read())
        {
            ReadSingleRow((IDataRecord)reader);
        }

        // Call Close when done reading.
        reader.Close();
    }
}

private static void ReadSingleRow(IDataRecord dataRecord)
{
    Console.WriteLine(String.Format("{0}, {1}", dataRecord[0], dataRecord[1]));
}

Private Sub ReadOrderData(ByVal connectionString As String)
    Dim queryString As String = _
        "SELECT OrderID, CustomerID FROM dbo.Orders;"

    Using connection As New SqlConnection(connectionString)
        Dim command As New SqlCommand(queryString, connection)
        connection.Open()

        Dim reader As SqlDataReader = command.ExecuteReader()

        ' Call Read before accessing data.
        While reader.Read()
            ReadSingleRow(CType(reader, IDataRecord))
        End While

        ' Call Close when done reading.
        reader.Close()
    End Using
End Sub

Private Sub ReadSingleRow(ByVal record As IDataRecord)
   Console.WriteLine(String.Format("{0}, {1}", record(0), record(1)))
End Sub

Remarks

The IDataReader and IDataRecord interfaces allow an inheriting class to implement a DataReader class, which provides a means of reading one or more forward-only streams of result sets. For more information about DataReader classes, see Retrieving Data Using a DataReader.

An application does not create an instance of the IDataReader interface directly, but creates an instance of a class that inherits IDataReader.

Classes that inherit IDataReader must implement the inherited members, and typically define additional members to add provider-specific functionality.

Changes made to a result set by another process or thread while data is being read may be visible to the user of a class that implements an IDataReader. However, the precise behavior is both provider and timing dependent.

Notes to Implementers

To promote consistency among .NET Framework data providers, name the inheriting class in the form Prv Command where Prv is the uniform prefix given to all classes in a specific .NET Framework data provider namespace. For example, Sql is the prefix of the SqlDataAdapter class in the System.Data.SqlClient namespace.

Users do not create an instance of a DataReader class directly. Instead, they obtain the DataReader instance through the ExecuteReader method of the Command object. Therefore, you should mark DataReader constructors as internal.

Properties

Depth	Gets a value indicating the depth of nesting for the current row.
FieldCount	Gets the number of columns in the current row. (Inherited from IDataRecord)
IsClosed	Gets a value indicating whether the data reader is closed.
Item[Int32]	Gets the column located at the specified index. (Inherited from IDataRecord)
Item[String]	Gets the column with the specified name. (Inherited from IDataRecord)
RecordsAffected	Gets the number of rows changed, inserted, or deleted by execution of the SQL statement.

Methods

Close()	Closes the IDataReader Object.
Dispose()	Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources. (Inherited from IDisposable)
GetBoolean(Int32)	Gets the value of the specified column as a Boolean. (Inherited from IDataRecord)
GetByte(Int32)	Gets the 8-bit unsigned integer value of the specified column. (Inherited from IDataRecord)
GetBytes(Int32, Int64, Byte[], Int32, Int32)	Reads a stream of bytes from the specified column offset into the buffer as an array, starting at the given buffer offset. (Inherited from IDataRecord)
GetChar(Int32)	Gets the character value of the specified column. (Inherited from IDataRecord)
GetChars(Int32, Int64, Char[], Int32, Int32)	Reads a stream of characters from the specified column offset into the buffer as an array, starting at the given buffer offset. (Inherited from IDataRecord)
GetData(Int32)	Returns an IDataReader for the specified column ordinal. (Inherited from IDataRecord)
GetDataTypeName(Int32)	Gets the data type information for the specified field. (Inherited from IDataRecord)
GetDateTime(Int32)	Gets the date and time data value of the specified field. (Inherited from IDataRecord)
GetDecimal(Int32)	Gets the fixed-position numeric value of the specified field. (Inherited from IDataRecord)
GetDouble(Int32)	Gets the double-precision floating point number of the specified field. (Inherited from IDataRecord)
GetFieldType(Int32)	Gets the Type information corresponding to the type of Object that would be returned from GetValue(Int32). (Inherited from IDataRecord)
GetFloat(Int32)	Gets the single-precision floating point number of the specified field. (Inherited from IDataRecord)
GetGuid(Int32)	Returns the GUID value of the specified field. (Inherited from IDataRecord)
GetInt16(Int32)	Gets the 16-bit signed integer value of the specified field. (Inherited from IDataRecord)
GetInt32(Int32)	Gets the 32-bit signed integer value of the specified field. (Inherited from IDataRecord)
GetInt64(Int32)	Gets the 64-bit signed integer value of the specified field. (Inherited from IDataRecord)
GetName(Int32)	Gets the name for the field to find. (Inherited from IDataRecord)
GetOrdinal(String)	Return the index of the named field. (Inherited from IDataRecord)
GetSchemaTable()	Returns a DataTable that describes the column metadata of the IDataReader. Returns null if the executed command returned no resultset, or after NextResult() returns false.
GetString(Int32)	Gets the string value of the specified field. (Inherited from IDataRecord)
GetValue(Int32)	Return the value of the specified field. (Inherited from IDataRecord)
GetValues(Object[])	Populates an array of objects with the column values of the current record. (Inherited from IDataRecord)
IsDBNull(Int32)	Return whether the specified field is set to null. (Inherited from IDataRecord)
NextResult()	Advances the data reader to the next result, when reading the results of batch SQL statements.
Read()	Advances the IDataReader to the next record.