what is need of connection open and close of execution in query in winform?

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WinForms

MySQL

hi friends,

In my form, lot of combo box is there. I want to load different table datas to combo box. I am trying to do that. but code is going on very long. Because of the connection open and close codings.

when i run two command in without close connection and open it throw

>

There is already an open DataReader associated with this Connection which must be closed first.<br />

Exception.

how to remove this open and close in my program

string MyConString = ConfigurationManager.ConnectionStrings["College_Management_System.Properties.Settings.cmsConnectionString"].ConnectionString;
          MySqlConnection connection = new MySqlConnection(MyConString);
          MySqlCommand command = connection.CreateCommand();
          MySqlDataReader Reader;
          command.CommandText = "select name from course_master";
          connection.Open();
          Reader = command.ExecuteReader();
          while (Reader.Read())
          {
              cmbo_course.Items.Add(Reader[0].ToString());
          }

          command.CommandText = "select name from country_master";
          Reader = command.ExecuteReader();
          while (Reader.Read())
          {
              cmbo_perCountry.Items.Add(Reader[0].ToString());
              cmbo_country.Items.Add(Reader[0].ToString());
          }
          connection.Close();

thanks in advance..