pluralsight-csharp-fundamentals/gradebook/src/GradeBook/Book.cs

using System;
using System.Collections.Generic;

namespace GradeBook
{
    public class Book
    {
        private List<double> grades;
        public string Name;

        public Book(string name)
        {
            Name = name;
            grades = new List<double>();
        }

        public void AddGrade(double grade)
        {
            this.grades.Add(grade);
        }

        public void AddLetterGrade(char letter)
        {
            switch (letter)
            {
                case 'A':
                    AddGrade(90);
                    break;
                case 'B':
                    AddGrade(80);
                    break;
                case 'C':
                    AddGrade(70);
                    break;
                default:
                    AddGrade(0);
                    break;
            }
        }

        public Statistics GetStatistics()
        {
            var result = new Statistics();
            result.Average = 0.0;
            result.highGrade = double.MinValue;
            result.lowGrade = double.MaxValue;

            foreach (var grade in this.grades)
            {
                result.lowGrade = Math.Min(grade, result.lowGrade);
                result.highGrade = Math.Max(grade, result.highGrade);
                result.Average += grade;
            }

            // var index = 0;
            // do
            // {
            //     result.lowGrade = Math.Min(grades[index], result.lowGrade);
            //     result.highGrade = Math.Max(grades[index], result.highGrade);
            //     result.Average += grades[index];
            //     index += 1;
            // } while (index < grades.Count);

            result.Average /= grades.Count;
            return result;
        }
    }
    
}