SqlDataReader Class

In This Topic

Reads a forward-only stream of rows from SQL Server.

Syntax

Visual Basic
C#

'Declaration
 
Public Class SqlDataReader 
   Inherits Devart.Common.DbDataReaderBase
   Implements System.Collections.IEnumerable, System.Data.IDataReader, System.Data.IDataRecord, System.IDisposable

public class SqlDataReader : Devart.Common.DbDataReaderBase, System.Collections.IEnumerable, System.Data.IDataReader, System.Data.IDataRecord, System.IDisposable

Remarks

To create a SqlDataReader, you must call the ExecuteReader method of the SqlCommand object, rather than directly using a constructor.

System.Data.Common.DbDataReader.IsClosed and Devart.Data.SqlShimDataReader.RecordsAffected are the only properties that you can call after the SqlDataReader is closed. In some cases, you must call Devart.Data.SqlShimDataReader.Close before you can call Devart.Data.SqlShimDataReader.RecordsAffected.

While the SqlDataReader is in use, the associated SqlConnection is busy serving the SqlDataReader, and no other operations can be performed on the SqlConnection other than closing it. This is the case until the Close method of the SqlDataReader is called. For example, you cannot retrieve output parameters until you call Close.

Example

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

csharp

public void ReadMyData(string myConnString)  {
        SqlConnection myConnection = new SqlConnection(myConnString);
        SqlCommand myCommand = (SqlCommand)myConnection.CreateCommand();
        myCommand.CommandText = "SELECT DeptNo, DName, Loc FROM Test.Dept";
        myConnection.Open();
        SqlDataReader myReader = myCommand.ExecuteReader();
        try {
                // Always call Read before accessing data.
                while (myReader.Read()) {
                Console.WriteLine(myReader.GetInt32(0).ToString() + " " + 
                myReader.GetString(1) + " " + myReader.GetString(2));
        }
        }
        finally {
                // always call Close when done reading.
                myReader.Close();

                // Close the connection when done with it.
                myConnection.Close();
        }
}

Visual Basic

Public Sub ReadMyData(ByVal myConnString As String)
        Dim myConnection As New SqlConnection(myConnString)
        Dim myCommand As SqlCommand = myConnection.CreateCommand()
                myCommand.CommandText = "SELECT DeptNo, DName, Loc FROM Test.Dept"
        myConnection.Open()
        Dim myReader As SqlDataReader = myCommand.ExecuteReader()
        Try
                ' Always call Read before accessing data.
                While myReader.Read()
                        Console.WriteLine(String.Concat(myReader.GetInt32(0).ToString(), " ", _
                        myReader.GetString(1), " ", myReader.GetString(2)))
                End While
        Finally
                ' always call Close when done reading.
                myReader.Close()

                        ' Close the connection when done with it.
                        myConnection.Close()
        End Try
End Sub

Inheritance Hierarchy

System.Object
   System.MarshalByRefObject
      System.Data.Common.DbDataReader
         Devart.Common.DbDataReaderBase
            Devart.Data.SqlServer.SqlDataReader

Reference

SqlDataReader Members
Devart.Data.SqlServer Namespace
SqlConnection Class
SqlCommand Class

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