我在PHPmyadmin中的查询有结果，但在C#中，a.read()不返回数据。
string query = "SELECT answer FROM tbl WHERE level = " + level + " AND subject = '" + subject[i] + "';";
MySqlCommand command = new MySqlCommand(query, connection);
connection.Open();
MySqlDataReader a = command.ExecuteReader();
while (a.Read())
{
//Do Some Things
}
connection.Close();
我认为查询字符串不正确，您可以使用string.format（）更好，这是代码：
string query = String.Format("SELECT answer FROM tbl WHERE level ={0} AND subject = '{1}'",level, subject[i].ToString());
从查询中删除单引号，使用下面的。
string query = "SELECT answer FROM tbl WHERE level = " + "x" + " AND subject = " + "y" + ";";
