/// <summary>
/// 执行指定数据库连接对象的命令,指定参数,返回结果集中的第一行第一列.
/// </summary>
/// <remarks>
/// 示例:
/// int orderCount = (int)ExecuteScalar(conn, CommandType.StoredProcedure, "GetOrderCount", new DB2Parameter("@prodid", 24));
/// </remarks>
/// <param name="connection">一个有效的数据库连接对象</param>
/// <param name="commandType">命令类型 (存储过程,命令文本或其它)</param>
/// <param name="commandText">存储过程名称或T-SQL语句</param>
/// <param name="commandParameters">分配给命令的DB2Paramter参数数组</param>
/// <returns>返回结果集中的第一行第一列</returns>
public static object ExecuteScalar(DB2Connection connection, CommandType commandType, string commandText, params DB2Parameter[] commandParameters)
{
if (connection == null) throw new ArgumentNullException("connection");
// 创建DB2Command命令,并进行预处理
DB2Command cmd = new DB2Command();
bool mustCloseConnection = false;
PrepareCommand(cmd, connection, (DB2Transaction)null, commandType, commandText, commandParameters, out mustCloseConnection);
// 执行DB2Command命令,并返回结果.
object retval = cmd.ExecuteScalar();
// 清除参数,以便再次使用.
cmd.Parameters.Clear();
if (mustCloseConnection)
connection.Close();
return retval;
}
/// <summary>
/// 执行指定数据库事务的命令,指定参数,返回结果集中的第一行第一列.
/// </summary>
/// <remarks>
/// 示例:
/// int orderCount = (int)ExecuteScalar(trans, CommandType.StoredProcedure, "GetOrderCount", new DB2Parameter("@prodid", 24));
/// </remarks>
/// <param name="transaction">一个有效的连接事务</param>
/// <param name="commandType">命令类型 (存储过程,命令文本或其它)</param>
/// <param name="commandText">存储过程名称或T-SQL语句</param>
/// <param name="commandParameters">分配给命令的DB2Paramter参数数组</param>
/// <returns>返回结果集中的第一行第一列</returns>
public static object ExecuteScalar(DB2Transaction transaction, CommandType commandType, string commandText, params DB2Parameter[] commandParameters)
{
if (transaction == null) throw new ArgumentNullException("transaction");
if (transaction != null && transaction.Connection == null) throw new ArgumentException("The transaction was rollbacked or commited, please provide an open transaction.", "transaction");
// 创建DB2Command命令,并进行预处理
DB2Command cmd = new DB2Command();
bool mustCloseConnection = false;
PrepareCommand(cmd, transaction.Connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection);
// 执行DB2Command命令,并返回结果.
object retval = cmd.ExecuteScalar();
// 清除参数,以便再次使用.
cmd.Parameters.Clear();
return retval;
}
/// <summary>
/// Returns the first column of the first row in the executed query. Additional rows and columns are ignored.
/// </summary>
/// <param name="command">Command (Text command or Stored Procedure)</param>
/// <param name="type">Type of command (text, stored procedure or table-direct)</param>
/// <returns></returns>
public object ExecuteScalar(string command, CommandType type)
{
object value = null;
try
{
using (DB2Connection connection = new DB2Connection(connectionString.ConnectionString))
{
using (DB2Command cmd = new DB2Command(command))
{
cmd.Connection = connection;
foreach (DB2Parameter parameter in Parameters)
{
cmd.Parameters.Add(parameter);
}
cmd.CommandType = type;
cmd.Connection.Open();
value = cmd.ExecuteScalar();
cmd.Connection.Close();
}
}
}
catch (Exception ex)
{
Error aError = new Error(ex.Source, ex.Message, GetCurrentMethod());
ErrorList.Add(aError);
}
return value;
}
