C# 读取mysql blob字段(两种方式)

while (reader.Read())
{
    //读取blob类型的字段
    //long len = reader.GetBytes(3, 0, null, 0, 0);//3为blob字段的索引（索引从0开始算）
    long len = reader.GetBytes(reader.GetOrdinal("blob字段名"), 0, null, 0, 0);
    byte[] buffer = new byte[len];
    len = reader.GetBytes(3, 0, buffer, 0, (int)len);
    string content = System.Text.Encoding.UTF8.GetString(buffer, 0, buffer.Length);  
   
}
while (reader.Read(