problem with the following code

I created the following class file:

public class DataAccess
      {
            public DataAccess()
            {
                  //
                  // TODO: Add constructor logic here
                  //
            }
            public static SqlDataReader GetDepartments()
            {
                  SqlConnection connection = new SqlConnection(connectionString);
                  SqlCommand command = new SqlCommand("GetTopNav", connection);
                  command.CommandType = CommandType.StoredProcedure;
                  connection.Open();
                  return command.ExecuteReader(CommandBehavior.CloseConnection);
            }
            private static string connectionString
            {
                  get
                  {
                        return ConfigurationSettings.AppSettings("ConnectionString");
                  }
            }
      }
}

I'm getting error on the following lines:

command.CommandType = CommandType.StoredProcedure;

return command.ExecuteReader(CommandBehavior.CloseConnection);

return ConfigurationSettings.AppSettings("ConnectionString");  //this references the connection string stored in the web.config file

Thanks for any help.