You haven't open the connection in your code, You should call
dbConn.Open();
It has nothing to do with using
statement.
string query = "SELECT * FROM teams ORDER BY name";
using(MySqlConnection dbConn = new MySqlConnection(conn))
{
MySqlCommand cmd = new MySqlCommand(query, dbConn);
dbConn.Open();//here **
MySqlDataReader dataReader = cmd.ExecuteReader();
using
statement only ensures that the your connection object will be disposed after the scope, it doesn't open the connection itself.