The IDbCommand interface enables an inheriting class to implement a Command class, which represents an SQL statement that is executed at a data source. For more information about Command classes, see Executing a Command (ADO.NET).

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

Classes that inherit IDbCommand must implement all inherited members, and typically define additional members to add provider-specific functionality. For example, the IDbCommand interface defines the ExecuteNonQuery method. In turn, the SqlCommand class inherits this method, and also defines the ExecuteXmlReader method.

To promote consistency among .NET Framework data providers, name the inheriting class in the form PrvClassname 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 SqlCommand class in the System.Data.SqlClient namespace.

When you inherit from the IDbCommand interface, you should implement the following constructors:

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

Public Sub ReadOrderData(ByVal connectionString As String)
    Dim commandText As String = "SELECT OrderID, CustomerID FROM dbo.Orders;"
    Using connection As New SqlConnection(connectionString)
        Using command As New SqlCommand(commandText, connection)
            connection.Open()
            Using reader As SqlDataReader = command.ExecuteReader()
                While reader.Read()
                    Console.WriteLine(String.Format("{0}, {1}", _
                      reader(0), reader(1)))
                End While
            End Using
        End Using
    End Using
End Sub

private static void ReadOrderData(string connectionString)
{
      string commandText = "SELECT OrderID, CustomerID FROM dbo.Orders;";
      using (SqlConnection connection = new SqlConnection(connectionString))
      {
            using (SqlCommand command = new SqlCommand(commandText, connection))
            {
                  connection.Open();
                  using (SqlDataReader reader = command.ExecuteReader())
                  {
                        while (reader.Read())
                        {
                              Console.WriteLine(String.Format("{0}, {1}", 
                                reader[0], reader[1]));
                        }
                  }
            }
      }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

.NET Framework

.NET Compact Framework

XNA Framework

Reference