C#读取Mysql blob字段 (转帖)

http://blog.csdn.net/config_man/article/details/6123191

开发环境：Windows XP Professional SP3、VS2008、Winform、MySQL5.0、MySQL.Data.dll 6.2.3.0

1、从硬盘上读取一图片，将其转化为流，然后存储到此BLOB字段中

private void button1_Click(object sender, EventArgs e)
{
    byte[] bytes = null;
    bytes = File.ReadAllBytes(@"C:/Documents and Settings/user/My Documents/My Pictures/11.jpg");
    using (MySql.Data.MySqlClient.MySqlConnection conn = new MySql.Data.MySqlClient.MySqlConnection())
    {
        conn.ConnectionString = ConfigurationManager.ConnectionStrings["test"].ConnectionString;
        MySql.Data.MySqlClient.MySqlCommand cmd = new MySql.Data.MySqlClient.MySqlCommand();
        cmd.CommandText = "insert into test(id,picture) values(@id,@picture)";
        cmd.CommandType = CommandType.Text;
        cmd.Parameters.Add("@id", MySql.Data.MySqlClient.MySqlDbType.Int32);
        cmd.Parameters.Add("@picture", MySql.Data.MySqlClient.MySqlDbType.Blob);

        cmd.Parameters[0].Value = 15;
        cmd.Parameters[1].Value = bytes;
        cmd.Connection = conn;
        conn.Open();

        int affectedrows = cmd.ExecuteNonQuery();

        cmd.Dispose();//此处可以不用调用,
        conn.Close();// 离开 using 块, connection 会自行关闭
    }
}

2、读取此BLOB字段，将其转化为图片显示在Picturebox控件上

private void button2_Click(object sender, EventArgs e)
{
    using (MySql.Data.MySqlClient.MySqlConnection conn = new MySql.Data.MySqlClient.MySqlConnection())
    {
        conn.ConnectionString = ConfigurationManager.ConnectionStrings["test"].ConnectionString;
        conn.Open();

        MySql.Data.MySqlClient.MySqlCommand cmd = new MySql.Data.MySqlClient.MySqlCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "select id,picture from test where id = 11";
        cmd.Connection = conn;

        System.Data.Common.DbDataReader reader = cmd.ExecuteReader();
        byte[] buffer = null;
        if (reader.HasRows)
        {
            reader.Read();
            long len = reader.GetBytes(1, 0, null, 0, 0);//1是picture
            buffer = new byte[len];
            len = reader.GetBytes(1, 0, buffer, 0, (int)len);

            System.IO.MemoryStream ms = new System.IO.MemoryStream(buffer);
            System.Drawing.Image iamge = System.Drawing.Image.FromStream(ms);
            pictureBox1.Image = iamge;
        }
    }
}

数据库相关文件配置在App.config中，如果不用配置文件，可以写成：

string remote = "Persist Security Info=False;database=数据库名;server=服务器IP;user id=用户名;pwd=密码";

然后conn.ConnectionString = remote;即可。

后记：

   之前在.net中用的mysql库是：MySQLDriverCS，但是一直没有搞定，而且用官方给的读取blob字段也失败。于是改用MySql.Data.dll ，注意Mysql.Data5.0版本不支持读取Blob字段，所以需要用较高版本，我用的是MySQL.Data.dll 6.2.3.0。

MySql.Data.dll 6.2.3.0下载地址：http://download.csdn.net/source/2968152

MySql.Data.dll 5.0.9.0下载地址：http://download.csdn.net/source/2968157