今天用C#类连接mysql数据库出现中文乱码具体解决方案如下：

用到的mysql表结构：

CREATE TABLE IF NOT EXISTS `tet` (
  `id` int(11) NOT NULL,
  `name` varchar(255) NOT NULL,
  `url` varchar(255) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

用到的mysql表数据：

INSERT INTO `tet` (`id`, `name`, `url`) VALUES
(1, '百度 ', 'http://www.baidu.com '),
(0, 'google ', 'http://www.google.com.hk '),
(3, '400电话 ', 'http://www.my400800.cn ');

一、查询结果没有问题，在查询条件中如果输入中文查询不到内容，用insert测试为，插入的内容是乱码

      首先在MySQL Command Line Client里面输入“SHOW VARIABLES LIKE 'character_set_%';”，可看到如下字符：

可以用如下连接字符串解决中文乱码问题

User Id=test;Host=localhost;Database=eczhou;password=test;charset='gb2312'

二、检索结果和插入内容都是乱码

用MySQL Command Line Client里面输入“SHOW VARIABLES LIKE 'character_set_%';”，可看到如下字符：

即便是连接字符串改成

User Id=test;Host=localhost;Database=eczhou;password=test;charset=utf8 检索的结果还是乱码

郁闷中。。。。。。。

然后用  show variables like 'collation%';显示结果是：

+----------------------+-----------------+
| Variable_name        | Value           |
+----------------------+-----------------+
| collation_connection | utf8_general_ci |
| collation_database   | utf8_general_ci |
| collation_server     | utf8_general_ci |
+----------------------+-----------------+

show variables like 'character%';

+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | latin1                     |
| character_set_connection | latin1                     |
| character_set_database   | utf8                       |
| character_set_filesystem | binary                     |
| character_set_results    | latin1                     |
| character_set_server     | utf8                       |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+

经过不懈努力的查找，终于找到问题了,问题就出在上面红色字体的编码上，我的解决方法如下：

连接字符串修改如下：

server=localhost;uid=root;pwd=root;database=test;Charset=latin1

c#代码如下：

 /// <summary>
        /// 执行查询语句，返回DataSet
        /// </summary>
        /// <param name="SQLString">查询语句</param>
        /// <returns>DataSet</returns>
        public static DataSet Query(string SQLString)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                DataSet ds = new DataSet();
            
                try
                {
                    connection.Open();
                    MySqlCommand M = new MySqlCommand("set names 'latin1'", connection);
                    M.ExecuteNonQuery();
                    //

                    MySqlDataAdapter da = new MySqlDataAdapter(SQLString, connection);
                    da.Fill(ds);
                }
                catch (MySqlException ex)
                {
                    connection.Close();
                    throw new Exception(ex.Message);
                }
                finally
                {
                    connection.Close();
                }
                DataTable dt = ds.Tables[0];
                foreach (DataRow dr in dt.Rows)
                {
                    for (int i = 0; i < dt.Columns.Count; i++)
                    {
                        dr[i] = Encoding.UTF8.GetString(Encoding.GetEncoding("latin1").GetBytes(dr[i].ToString()));
                    }


                }

                return ds;
            }
        }

一定要注意上面的红色字体。