//===============================================================================
// This file is based on the Microsoft Data Access Application Block for .NET
// For more information please go to 
// http://msdn.microsoft.com/library/en-us/dnbda/html/daab-rm.asp
//===============================================================================

using System;
using System.Configuration;
using System.Data;
using MySqlConnector;
using System.Collections;

/// <summary>
/// The MySqlHelper class is intended to encapsulate high performance, 
/// scalable best practices for common uses of MySqlConnector.
/// </summary>
public abstract class MySqlHelper
{
    //Database connection strings
    public static readonly string ConnectionString = "";

    // Hashtable to store cached parameters
    private static Hashtable parmCache = Hashtable.Synchronized(new Hashtable());

    /// <summary>
    /// Execute a MySqlCommand (that returns no resultset) against the database specified in the connection string 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new MySqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="connectionString">a valid connection string for a MySqlConnection</param>
    /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="commandText">the stored procedure name or T-SQL command</param>
    /// <param name="commandParameters">an array of MySqlParamters used to execute the command</param>
    /// <returns>an int representing the number of rows affected by the command</returns>
    public static int ExecuteNonQuery(string connectionString, CommandType cmdType, string cmdText, params MySqlParameter[] commandParameters)
    {
        MySqlCommand cmd = new MySqlCommand();

        using (MySqlConnection conn = new MySqlConnection(connectionString))
        {
            PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
            int val = cmd.ExecuteNonQuery();
            cmd.Parameters.Clear();
            return val;
        }
    }

    /// <summary>
    /// Execute a MySqlCommand (that returns no resultset) against an existing database connection 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new MySqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="conn">an existing database connection</param>
    /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="commandText">the stored procedure name or T-SQL command</param>
    /// <param name="commandParameters">an array of MySqlParamters used to execute the command</param>
    /// <returns>an int representing the number of rows affected by the command</returns>
    public static int ExecuteNonQuery(MySqlConnection connection, CommandType cmdType, string cmdText, params MySqlParameter[] commandParameters)
    {
        MySqlCommand cmd = new MySqlCommand();

        PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
        int val = cmd.ExecuteNonQuery();
        cmd.Parameters.Clear();
        return val;
    }

    /// <summary>
    /// Execute a MySqlCommand (that returns no resultset) using an existing SQL Transaction 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new MySqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="trans">an existing sql transaction</param>
    /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="commandText">the stored procedure name or T-SQL command</param>
    /// <param name="commandParameters">an array of MySqlParamters used to execute the command</param>
    /// <returns>an int representing the number of rows affected by the command</returns>
    public static int ExecuteNonQuery(MySqlTransaction trans, CommandType cmdType, string cmdText, params MySqlParameter[] commandParameters)
    {
        MySqlCommand cmd = new MySqlCommand();
        PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, commandParameters);
        int val = cmd.ExecuteNonQuery();
        cmd.Parameters.Clear();
        return val;
    }

    /// <summary>
    /// Execute a MySqlCommand that returns a resultset against the database specified in the connection string 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  MySqlDataReader r = ExecuteReader(connString, CommandType.StoredProcedure, "PublishOrders", new MySqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="connectionString">a valid connection string for a MySqlConnection</param>
    /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="commandText">the stored procedure name or T-SQL command</param>
    /// <param name="commandParameters">an array of MySqlParamters used to execute the command</param>
    /// <returns>A MySqlDataReader containing the results</returns>
    public static MySqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params MySqlParameter[] commandParameters)
    {
        MySqlCommand cmd = new MySqlCommand();
        MySqlConnection conn = new MySqlConnection(connectionString);

        // we use a try/catch here because if the method throws an exception we want to 
        // close the connection throw code, because no datareader will exist, hence the 
        // commandBehaviour.CloseConnection will not work
        try
        {
            PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
            MySqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            cmd.Parameters.Clear();
            return rdr;
        }
        catch
        {
            conn.Close();
            throw;
        }
    }

    /// <summary>
    /// Ö´ÐвéѯÓï¾ä£¬·µ»ØDataSet
    /// </summary>
    /// <param name="SQLString">²éѯÓï¾ä</param>
    /// <returns>DataSet</returns>
    public static DataSet Query(string connectionString, string SQLString)
    {
        using (MySqlConnection connection = new MySqlConnection(connectionString))
        {
            DataSet ds = new DataSet();
            try
            {
                connection.Open();
                MySqlDataAdapter command = new MySqlDataAdapter(SQLString, connection);
                command.Fill(ds, "ds");
            }
            catch (MySqlException ex)
            {
                throw new Exception(ex.Message);
            }
            return ds;
        }
    }

    /// <summary>
    /// Execute a MySqlCommand that returns the first column of the first record against the database specified in the connection string 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new MySqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="connectionString">a valid connection string for a MySqlConnection</param>
    /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="commandText">the stored procedure name or T-SQL command</param>
    /// <param name="commandParameters">an array of MySqlParamters used to execute the command</param>
    /// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
    public static object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText, params MySqlParameter[] commandParameters)
    {
        MySqlCommand cmd = new MySqlCommand();

        using (MySqlConnection connection = new MySqlConnection(connectionString))
        {
            PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }
    }

    /// <summary>
    /// Execute a MySqlCommand that returns the first column of the first record against an existing database connection 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new MySqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="conn">an existing database connection</param>
    /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="commandText">the stored procedure name or T-SQL command</param>
    /// <param name="commandParameters">an array of MySqlParamters used to execute the command</param>
    /// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
    public static object ExecuteScalar(MySqlConnection connection, CommandType cmdType, string cmdText, params MySqlParameter[] commandParameters)
    {
        MySqlCommand cmd = new MySqlCommand();

        PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
        object val = cmd.ExecuteScalar();
        cmd.Parameters.Clear();
        return val;
    }

    /// <summary>
    /// add parameter array to the cache
    /// </summary>
    /// <param name="cacheKey">Key to the parameter cache</param>
    /// <param name="cmdParms">an array of MySqlParamters to be cached</param>
    public static void CacheParameters(string cacheKey, params MySqlParameter[] commandParameters)
    {
        parmCache[cacheKey] = commandParameters;
    }

    /// <summary>
    /// Retrieve cached parameters
    /// </summary>
    /// <param name="cacheKey">key used to lookup parameters</param>
    /// <returns>Cached MySqlParamters array</returns>
    public static MySqlParameter[] GetCachedParameters(string cacheKey)
    {
        MySqlParameter[] cachedParms = (MySqlParameter[])parmCache[cacheKey];

        if (cachedParms == null)
            return null;

        MySqlParameter[] clonedParms = new MySqlParameter[cachedParms.Length];

        for (int i = 0, j = cachedParms.Length; i < j; i++)
            clonedParms[i] = (MySqlParameter)((ICloneable)cachedParms[i]).Clone();

        return clonedParms;
    }

    /// <summary>
    /// Prepare a command for execution
    /// </summary>
    /// <param name="cmd">MySqlCommand object</param>
    /// <param name="conn">MySqlConnection object</param>
    /// <param name="trans">MySqlTransaction object</param>
    /// <param name="cmdType">Cmd type e.g. stored procedure or text</param>
    /// <param name="cmdText">Command text, e.g. Select * from Products</param>
    /// <param name="cmdParms">MySqlParameters to use in the command</param>
    private static void PrepareCommand(MySqlCommand cmd, MySqlConnection conn, MySqlTransaction trans, CommandType cmdType, string cmdText, MySqlParameter[] cmdParms)
    {
        if (conn.State != ConnectionState.Open)
            conn.Open();

        cmd.Connection = conn;
        cmd.CommandText = cmdText;

        if (trans != null)
            cmd.Transaction = trans;

        cmd.CommandType = cmdType;

        if (cmdParms != null)
        {
            foreach (MySqlParameter parm in cmdParms)
                cmd.Parameters.Add(parm);
        }
    }
}