重构DAL代码以支持存储过程

    private static readonly string dataProvider = ConfigurationManager.AppSettings.Get("Provider");
    private static readonly DbProviderFactory factory = DbProviderFactories.GetFactory(dataProvider);
    private static readonly string connectionString = ConfigurationManager.ConnectionStrings[dataProvider].ConnectionString;
    /// <summary>
    /// Executes Update statements in the database.
    /// </summary>
    /// <param name="sql">Sql statement.</param>
    /// <returns>Number of rows affected.</returns>
    public static int Update(string sql)
    {
        using (DbConnection connection = factory.CreateConnection())
        {
            connection.ConnectionString = connectionString;

            using (DbCommand command = factory.CreateCommand())
            {
                command.Connection = connection;
                command.CommandText = sql;

                connection.Open();
                return command.ExecuteNonQuery();
            }
        }
    }
    private static readonly string dataProvider