Input is not recognized when typed in by user

Question

So, I am a new student in Software and I'm doing my assignment, this may seem like a simple question but it is wrecking my head.

The assignment is for the user to input 6 school subject and the grade they got for each, then to calculate the grades into points and display. I feel that I have the skeleton of the code done, however when I run the program no matter what input I put in the answer always seems to be invalid.

Thanks for your help, Joe

Here is the code I am using, its being used in Visual Studio.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace caoAssignment
{
    class Program
    {
        static void Main(string[] args)
        {
            // Delcaring variables //
            string subIn, sub1, sub2, sub3, sub4, sub5, sub6;
            string gradeIn, grade1, grade2, grade3, grade4, grade5, grade6;
            int pointsIn, points1, points2, points3, points4, points5, points6;
            int x;
            string doAgain = "";

            // Getting the user to input necessary information. 2 peices needed. 

            do
            {
                x = 1;
                while (x <= 6)
                {
                    Console.WriteLine("Please enter a subject ");
                    subIn = Console.ReadLine();

                    Console.WriteLine("Please enter the grade you got in that                      subject (H1 - O8) ");
                    gradeIn = Console.ReadLine();

                    // Processing the grades in points //

                    if (gradeIn == "H1")
                        pointsIn = 100;

                    if (gradeIn == "H2")
                        pointsIn = 88;

                    if (gradeIn == "H3")
                        pointsIn = 77;

                    if (gradeIn == "H4")
                        pointsIn = 66;

                    if (gradeIn == "H5")
                        pointsIn = 56;

                    if (gradeIn == "H6")
                        pointsIn = 46;

                    if (gradeIn == "H7")
                        pointsIn = 37;

                    if (gradeIn == "H8")
                        pointsIn = 0;

                    if (gradeIn == "O1")
                        pointsIn = 56;

                    if (gradeIn == "O2")
                        pointsIn = 46;

                    if (gradeIn == "O3")
                        pointsIn = 37;

                    if (gradeIn == "O4")
                        pointsIn = 28;

                    if (gradeIn == "O5")
                        pointsIn = 20;

                    if (gradeIn == "O6")
                        pointsIn = 12;

                    if (gradeIn == "O7")
                        pointsIn = 0;

                    if (gradeIn == "O8")
                        pointsIn = 0;

                    else
                        Console.WriteLine("Input is wrong, please redo. ");


                    // Assigning each grade,subject and points depending on what X is //
                    if (x == 1)
                    {
                        subIn = sub1;
                        gradeIn = grade1;
                        pointsIn = points1;

                    }

                    if (x == 2)
                    {
                        subIn = sub2;
                        gradeIn = grade2;
                        pointsIn = points2;

                    }

                    if (x == 3)
                    {
                        subIn = sub3;
                        gradeIn = grade3;
                        pointsIn = points3;

                    }

                    if (x == 4)
                    {
                        subIn = sub4;
                        gradeIn = grade4;
                        pointsIn = points4;

                    }

                    if (x == 5)
                    {
                        subIn = sub5;
                        gradeIn = grade5;
                        pointsIn = points5;

                    }

                    if (x == 6)
                    {
                        subIn = sub6;
                        gradeIn = grade6;
                        pointsIn = points6;

                    }

                    x++;
                } // End of the while loop

                Console.WriteLine("Do again? (Y/N) ");
                doAgain = Console.ReadLine();

            } // End of the do loop
            while (doAgain == "Y"); 

            // Command to keep the program open for the user //
            Console.ReadKey();

        }
    }
}

Answer 1

Take a look at this part of the code:

if (gradeIn == "O7")
    pointsIn = 0;

if (gradeIn == "O8")
    pointsIn = 0;
else
    Console.WriteLine("Input is wrong, please redo. ");

What happens if grade is not "08"? The else statement is only applied to the last if statement. Also a good rule of thumb is to always add curly braces after if, else, etc, to indicate the scope and avoid mistakes.

If you chain the if statements with else, you are telling the program that the next if is only going to apply if the previous was not applied.

if (gradeIn == "O7")
{
    pointsIn = 0;
}
else if (gradeIn == "O8")
{
    pointsIn = 0;
}
else
{
    Console.WriteLine("Input is wrong, please redo. ");
}

When comparing strings using the == operator, the comparison is case sensitive. To make it case insensitive, use the overloaded string.Equals method:

if(string.Equals(gradeIn, "O7", StringComparison.OrdinalIgnoreCase))

Answer 2

Firstly, project should not compile, as code is trying to use unassigned variables. Sub1

//Assigning each grade,subject and points depending on what X is 
if (x == 1)
{
subIn = sub1;
gradeIn = grade1;
pointsIn = points1;
}

Secondly

subIn = sub2;

This should be the other way. The first value is the variable you want to assign second value.