// GradeBook class uses switch statement to count letter grades.
using System;

public class GradeBook
{
   private int total;           // sum of grades
   private int gradeCounter;    // number of grades entered
   private int aCount;          // count of A grades
   private int bCount;          // count of B grades
   private int cCount;          // count of C grades
   private int dCount;          // count of D grades
   private int fCount;          // count of F grades

   // automatic property CourseName
   public string CourseName { get; set; }

   // constructor initializes automatic property CourseName; 
   // int instance variables are initialized to 0 by default
   public GradeBook( string name )
   {
      CourseName = name;
   }

   // display a welcome message to the GradeBook user
   public void DisplayMessage()
   {
      // CourseName gets the name of the course
      Console.WriteLine( "Welcome to the grade book for\n{0}!\n",
                         CourseName );
   }

   // input arbitrary number of grades from user
   public void InputGrades()
   {
      int grade;    // grade entered by user
      string input; // text entered by the user

      Console.WriteLine( "{0}\n{1}",
                         "Enter the integer grades in the range 0-100.",
                         "Type <Ctrl> z and press Enter to terminate input:" );

      input = Console.ReadLine();

      // loop until user enters the end-of-file indicator (<Ctrl> z)
      while ( input != null )
      {
         grade = Convert.ToInt32( input );  // read grade off user input
         total += grade;                    // add grade to total
         ++gradeCounter;                    // increment number of grades

         // call method to increment appropriate counter
         IncrementLetterGradeCounter( grade );

         input = Console.ReadLine(); // read user input
      } // end while 
   } // end method InputGrades

   // add 1 to appropriate counter for specified grade
   private void IncrementLetterGradeCounter( int grade )
   {
      // determine which grade was entered
      switch ( grade / 10 )
      {
         case 9:        // grade was in the 90s
         case 10:       // grade was 100 
            ++aCount;   // increment aCount
            break;      // necessary to exit switch
         case 8:        // grade was between 80 and 89
            ++bCount;   // increment bCount    
            break;      // exit switch
         case 7:        // grade was between 70 and 79
            ++cCount;   // increment cCount    
            break;      // exit switch
         case 6:        // grade was between 60 and 69
            ++dCount;   // increment dCount    
            break;      // exit switch
         default:       // grade was less than 60
            ++fCount;   // increment fCount       
            break;      // exit switch
      }
   } // end method IncrementLetterGradeCounter

   // display a report based on the grades entered by the user 
   public void DisplayGradeReport()
   {
      Console.WriteLine( "\nGrade Report:" );

      // if user entered at least one grade...
      if (gradeCounter != 0)
      {
          // calculate average of all grades entered
          double average = (double)total / gradeCounter;

          // output summary of results
          Console.WriteLine("Total of the {0} grades entered is {1}",
                                                 gradeCounter, total);
          Console.WriteLine("Class average is {0:F}", average);
          Console.WriteLine("{0}A: {1}\nB: {2}\nC: {3}\nD: {4}\nF: {5}",
                             "Number of students who received each grade:\n",
                             aCount,  // display number of A grades
                             bCount,  // display number of B grades
                             cCount,  // display number of C grades 
                             dCount,  // display number of D grades
                             fCount); // display number of F grades
      }
      else // no grades were entered, so output appropriate message
      {
          Console.WriteLine("No grades were entered");
      }
   } // end method DisplayGradeReport
} // end class GradeBook