OleDbCommand.ExecuteReader Method

Definition

Namespace:

System.Data.OleDb

Assembly:

System.Data.OleDb.dll

Package:

System.Data.OleDb v9.0.0-rc.2.24473.5

Sends the CommandText to the Connection and builds an OleDbDataReader.

Overloads

ExecuteReader()	Sends the CommandText to the Connection and builds an OleDbDataReader.
ExecuteReader(CommandBehavior)	Sends the CommandText to the Connection, and builds an OleDbDataReader using one of the CommandBehavior values.

ExecuteReader()

Sends the CommandText to the Connection and builds an OleDbDataReader.

public:
 System::Data::OleDb::OleDbDataReader ^ ExecuteReader();

public System.Data.OleDb.OleDbDataReader ExecuteReader ();

override this.ExecuteReader : unit -> System.Data.OleDb.OleDbDataReader

Public Function ExecuteReader () As OleDbDataReader

Returns

OleDbDataReader

An OleDbDataReader object.

Exceptions

InvalidOperationException

Cannot execute a command within a transaction context that differs from the context in which the connection was originally enlisted.

Examples

The following example creates an OleDbCommand, and then executes it by passing a string that is an SQL SELECT statement, and a string to use to connect to the data source.

public void CreateReader(string connectionString, string queryString)
{
    using (OleDbConnection connection = new OleDbConnection(connectionString))
    {
        OleDbCommand command = new OleDbCommand(queryString, connection);
        connection.Open();
        OleDbDataReader reader = command.ExecuteReader();

        while (reader.Read())
        {
            Console.WriteLine(reader[0].ToString());
        }
        reader.Close();
    }
}

Public Sub CreateReader(ByVal connectionString As String, _
    ByVal queryString As String)

    Using connection As New OleDbConnection(connectionString)
        Dim command As New OleDbCommand(queryString, connection)

        connection.Open()

        Dim reader As OleDbDataReader = command.ExecuteReader()
        While reader.Read()
            Console.WriteLine(reader(0).ToString())
        End While
        reader.Close()
    End Using
End Sub

Remarks

When the CommandType property is set to StoredProcedure, the CommandText property should be set to the name of the stored procedure. The command executes this stored procedure when you call ExecuteReader.

Before you close the OleDbConnection, first close the OleDbDataReader object. You must also close the OleDbDataReader object if you plan to reuse an OleDbCommand object.

See also

• Working with Commands

ExecuteReader(CommandBehavior)

Sends the CommandText to the Connection, and builds an OleDbDataReader using one of the CommandBehavior values.

public:
 System::Data::OleDb::OleDbDataReader ^ ExecuteReader(System::Data::CommandBehavior behavior);

public System.Data.OleDb.OleDbDataReader ExecuteReader (System.Data.CommandBehavior behavior);

override this.ExecuteReader : System.Data.CommandBehavior -> System.Data.OleDb.OleDbDataReader

Public Function ExecuteReader (behavior As CommandBehavior) As OleDbDataReader

Parameters

behavior

CommandBehavior

One of the CommandBehavior values.

Returns

OleDbDataReader

An OleDbDataReader object.

Exceptions

InvalidOperationException

Cannot execute a command within a transaction context that differs from the context in which the connection was originally enlisted.

Examples

The following example creates an OleDbCommand, and then executes it by passing a string that is a Transact-SQL SELECT statement, and a string to use to connect to the data source. CommandBehavior is set to CloseConnection.

public void CreateMyOleDbDataReader(string queryString,string connectionString)
{
   OleDbConnection connection = new OleDbConnection(connectionString);
   OleDbCommand command = new OleDbCommand(queryString, connection);
   connection.Open();
   OleDbDataReader reader = command.ExecuteReader(CommandBehavior.CloseConnection);
   while(reader.Read())
   {
      Console.WriteLine(reader.GetString(0));
   }
   reader.Close();
   //Implicitly closes the connection because CommandBehavior.CloseConnection was specified.
}

Public Sub CreateMyOleDbDataReader(queryString As String, _
    connectionString As String)
    Dim connection As New OleDbConnection(connectionString)
    Dim command As New OleDbCommand(queryString, connection)
    connection.Open()
    Dim reader As OleDbDataReader = command.ExecuteReader(CommandBehavior.CloseConnection)
    While reader.Read()
        Console.WriteLine(reader.GetString(0))
    End While
    reader.Close()
    'Implicitly closes the connection because CommandBehavior.CloseConnection was specified.
 End Sub

Remarks

When you specify SingleRow with the ExecuteReader method of the OleDbCommand object, the .NET Framework Data Provider for OLE DB performs binding using the OLE DB IRow interface if it is available. Otherwise, it uses the IRowset interface. If your SQL statement is expected to return only a single row, specifying SingleRow can also improve application performance.

When the CommandType property is set to StoredProcedure, the CommandText property should be set to the name of the stored procedure. The command executes this stored procedure when you call ExecuteReader.

The OleDbDataReader supports a special mode that enables large binary values to be read efficiently. For more information, see the SequentialAccess setting for CommandBehavior.

Before you close the OleDbConnection, first close the OleDbDataReader object. You must also close the OleDbDataReader object if you plan to reuse an OleDbCommand object. If the OleDbDataReader is created with CommandBehavior set to CloseConnection, closing the OleDbDataReader closes the connection automatically.

See also

• Working with Commands