/// <summary>
/// This method is used to attach array of TurboDBParameters to a TurboDBCommand.
///
/// This method will assign a value of DbNull to any parameter with a direction of
/// InputOutput and a value of null.
///
/// This behavior will prevent default values from being used, but
/// this will be the less common case than an intended pure output parameter (derived as InputOutput)
/// where the user provided no input value.
/// </summary>
/// <param name="command">The command to which the parameters will be added</param>
/// <param name="commandParameters">An array of TurboDBParameters to be added to command</param>
private static void AttachParameters(TurboDBCommand command, TurboDBParameter[] commandParameters)
{
if( command == null ) throw new ArgumentNullException( "command" );
if( commandParameters != null )
{
foreach (TurboDBParameter p in commandParameters)
{
if( p != null )
{
// Check for derived output value with no value assigned
if ( ( p.Direction == ParameterDirection.InputOutput ||
p.Direction == ParameterDirection.Input ) &&
(p.Value == null))
{
p.Value = DBNull.Value;
}
command.Parameters.Add(p);
}
}
}
}
/// <summary>
/// Create and prepare a TurboDBCommand, and call ExecuteReader with the appropriate CommandBehavior.
/// </summary>
/// <remarks>
/// If we created and opened the connection, we want the connection to be closed when the DataReader is closed.
///
/// If the caller provided the connection, we want to leave it to them to manage.
/// </remarks>
/// <param name="connection">A valid TurboDBConnection, on which to execute this command</param>
/// <param name="transaction">A valid TurboDBTransaction, or 'null'</param>
/// <param name="commandType">The CommandType (TableDirect, Text)</param>
/// <param name="commandText">The T-SQL command</param>
/// <param name="commandParameters">An array of TurboDBParameters to be associated with the command or 'null' if no parameters are required</param>
/// <param name="connectionOwnership">Indicates whether the connection parameter was provided by the caller, or created by TurboDBHelper</param>
/// <returns>TurboDBDataReader containing the results of the command</returns>
private static TurboDBDataReader ExecuteReader(TurboDBConnection connection, TurboDBTransaction transaction, CommandType commandType, string commandText, TurboDBParameter[] commandParameters, TurboDBConnectionOwnership connectionOwnership)
{
if( connection == null ) throw new ArgumentNullException( "connection" );
bool mustCloseConnection = false;
// Create a command and prepare it for execution
TurboDBCommand cmd = new TurboDBCommand();
try
{
PrepareCommand(cmd, connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection );
// Create a reader
TurboDBDataReader dataReader;
// Call ExecuteReader with the appropriate CommandBehavior
if (connectionOwnership == TurboDBConnectionOwnership.External)
{
dataReader = cmd.ExecuteReader();
}
else
{
dataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
}
// Detach the TurboDBParameters from the command object, so they can be used again.
// HACK: There is a problem here, the output parameter values are fletched
// when the reader is closed, so if the parameters are detached from the command
// then the TurboDBReader can´t set its values.
// When this happen, the parameters can´t be used again in other command.
bool canClear = true;
foreach(TurboDBParameter commandParameter in cmd.Parameters)
{
if (commandParameter.Direction != ParameterDirection.Input)
canClear = false;
}
if (canClear)
{
cmd.Parameters.Clear();
}
return dataReader;
}
catch
{
if( mustCloseConnection )
connection.Close();
throw;
}
}
/// <summary>
/// This method opens (if necessary) and assigns a connection, transaction, command type and parameters
/// to the provided command
/// </summary>
/// <param name="command">The TurboDBCommand to be prepared</param>
/// <param name="connection">A valid TurboDBConnection, on which to execute this command</param>
/// <param name="transaction">A valid TurboDBTransaction, or 'null'</param>
/// <param name="commandType">The CommandType (TableDirect, Text)</param>
/// <param name="commandText">The T-SQL command</param>
/// <param name="commandParameters">An array of TurboDBParameters to be associated with the command or 'null' if no parameters are required</param>
/// <param name="mustCloseConnection"><c>true</c> if the connection was opened by the method, otherwose is false.</param>
private static void PrepareCommand(TurboDBCommand command, TurboDBConnection connection, TurboDBTransaction transaction, CommandType commandType, string commandText, TurboDBParameter[] commandParameters, out bool mustCloseConnection )
{
if( command == null ) throw new ArgumentNullException( "command" );
if(commandType == CommandType.StoredProcedure ) throw new ArgumentException("Stored Procedures are not supported.");
// If the provided connection is not open, we will open it
if (connection.State != ConnectionState.Open)
{
mustCloseConnection = true;
connection.Open();
}
else
{
mustCloseConnection = false;
}
// Associate the connection with the command
command.Connection = connection;
// Set the command text (SQL statement)
command.CommandText = commandText;
// If we were provided a transaction, assign it
if (transaction != null)
{
if( transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
command.Transaction = transaction;
}
// Set the command type
command.CommandType = commandType;
// Attach the command parameters if they are provided
if (commandParameters != null)
{
AttachParameters(command, commandParameters);
}
return;
}
