int gradeLevel = Console.ReadLine();

1-8-registration.cs(2,20): error CS0029: Cannot implicitly convert type 'string' to 'int'
The build failed. Fix the build errors and run again.

int gradeLevel = int.Parse(Console.ReadLine());

Grade level: 8 [Enter]
Next year you'll be in grade 9.

int.Parse(Console.ReadLine())

double average = double.Parse(Console.ReadLine());

Average raised per student? 18.4 [Enter]
Average 18.4 raised

double average = 18.4;
double threeFundraisers = average * 3;

Console.WriteLine($"Three fundraisers: {threeFundraisers}");

Three fundraisers: 55.199999999999996

Three fundraisers: 55.199999999999996

Console.WriteLine($"Three fundraisers: {threeFundraisers:F2}");

Three fundraisers: 55.20

Console.WriteLine($"Average: {average} raised");
Console.WriteLine($"Average: {average:F2} raised");

Average: 18.4 raised
Average: 18.40 raised

Console.WriteLine($"Rounded: {threeFundraisers:F2}");
Console.WriteLine($"Raw:     {threeFundraisers}");

Rounded: 55.20
Raw:     55.199999999999996

int students = int.Parse(Console.ReadLine());

How many students signed up? seven [Enter]
Unhandled exception. System.FormatException: The input string 'seven' was not in a correct format.
   at System.Number.ThrowFormatException[TChar](ReadOnlySpan`1 value)
   at System.Int32.Parse(String s)
   at Program.<Main>$(String[] args) in 1-9-planner.cs:line 2

How many students signed up? seven [Enter]
Unhandled exception. System.FormatException: The input string 'seven' was not in a correct format.
   at System.Number.ThrowFormatException[TChar](ReadOnlySpan`1 value)
   at System.Int32.Parse(String s)
   at Program.<Main>$(String[] args) in 1-9-planner.cs:line 2

1-8-registration.cs(2,20): error CS0029: Cannot implicitly convert type 'string' to 'int'
The build failed. Fix the build errors and run again.

How many students signed up? seven [Enter]
Unhandled exception. System.FormatException: The input string 'seven' was not in a correct format.
   at System.Number.ThrowFormatException[TChar](ReadOnlySpan`1 value)
   at System.Int32.Parse(String s)
   at Program.<Main>$(String[] args) in 1-9-planner.cs:line 2

'F' → Fullscreen

Build

Open your 1-8-registration program for Task 1. Everything after that goes in a new program named 1-9-planner.

Task 1: Finish Last Session

• Uncomment the two lines you left broken at the end of Activity 1.8.
• Add int.Parse around the Console.ReadLine call and run it.
• Compare it with the guess you wrote down. Being wrong costs nothing; not having guessed costs the session.

1
Console.Write("Grade level: ");
2
int gradeLevel = int.Parse(Console.ReadLine());
3

4
Console.WriteLine($"Next year you'll be in grade {gradeLevel + 1}.");

Task 2: The Field Trip Planner

• Start 1-9-planner empty. Ask for the number of students and the bus size, then work out the buses.
• This is the same division-and-remainder shape as Activity 1.6's raid math, taken out of hardcoded numbers and into input. Run it with 47 and 6 first and check you still get 7 and 5.
• Then run it again with numbers of your own choosing.

1
Console.Write("How many students signed up? ");
2
int students = int.Parse(Console.ReadLine());
3

4
Console.Write("How many per bus? ");
5
int perBus = int.Parse(Console.ReadLine());
6

7
int fullBuses = students / perBus;
8
int leftOver = students % perBus;
9

10
Console.WriteLine();
11
Console.WriteLine("=== FIELD TRIP PLAN ===");
12
Console.WriteLine($"Students:   {students}");
13
Console.WriteLine($"Full buses: {fullBuses}");
14
Console.WriteLine($"Left over:  {leftOver}");

Task 3: Two More Questions, and Making Them Readable

• Ask for a bus fee and compute the total cost.
• Ask for an average amount raised per student, which is not a whole number. Use double.Parse for that one.
• Work out what three fundraisers like that would raise in total, and print that too.
• Run it with no :F2 anywhere first. Type 18.4 for the average. Write down exactly what the three-fundraiser number looks like — all of it.
• Then add :F2 to the average and the projection, and run it again. Write down what each one says now.
• Note: the green lines marked with a + sign are new. Do not type the + sign.

1
Console.Write("How many students signed up? ");
2
int students = int.Parse(Console.ReadLine());
3

4
Console.Write("How many per bus? ");
5
int perBus = int.Parse(Console.ReadLine());
6

7
Console.Write("Bus fee? ");
8
int busFee = int.Parse(Console.ReadLine());
9

10
Console.Write("Average raised per student? ");
11
double average = double.Parse(Console.ReadLine());
12

13
int fullBuses = students / perBus;
14
int leftOver = students % perBus;
15
double threeFundraisers = average * 3;
16

17
Console.WriteLine();
18
Console.WriteLine("=== FIELD TRIP PLAN ===");
19
Console.WriteLine($"Students:   {students}");
20
Console.WriteLine($"Full buses: {fullBuses}");
21
Console.WriteLine($"Left over:  {leftOver}");
22
Console.WriteLine($"Bus cost:   {fullBuses * busFee}");
23
Console.WriteLine($"Average:    {average:F2} raised");
24
Console.WriteLine($"Three fundraisers: {threeFundraisers:F2}");

Task 4: Break It on Purpose

Five runs of your finished planner. Write down exactly what happens each time, copied from the screen.

1. For the number of students, type seven instead of 7.
2. For the number of students, press Enter without typing anything.
3. For the number of students, type 3.5.
4. For the number of students, type 47 with a space before and after it.
5. For the average raised per student, type 3.5.

Three of these stop the program and two do not. For each one that stops, write down the line number it names.

Challenge (Optional): Where Would You Put the Check?

• You cannot fix Task 4 yet. Deciding what to do about bad input needs an if, and that is session 12.
• Write a comment saying where in your program a check would have to go, and what it would have to ask.
• Describing it in plain English is the exercise. No code.

Checkpoint

Your finished planner should run like this.

How many students signed up? 47 [Enter]
How many per bus? 6 [Enter]
Bus fee? 25 [Enter]
Average raised per student? 18.4 [Enter]

=== FIELD TRIP PLAN ===
Students:   47
Full buses: 7
Left over:  5
Bus cost:   175
Average:    18.40 raised
Three fundraisers: 55.20

• Every number in the summary came from an answer, not from your code.
• 47 and 6 still produce 7 and 5.
• The average uses double.Parse, and the rest use int.Parse.
• Both decimal lines print with exactly two decimal places, and you have the unformatted three-fundraiser number written down.
• All five Task 4 results are written down, with line numbers where the program stopped.

Reflection

Answer the following questions before submitting your work.

1. Describe what happens in int.Parse(Console.ReadLine()), in the order it happens. Name what each part hands to the next.
2. Activity 1.8's mistake was refused before the program ran. This session's only appears when somebody types the wrong thing. Which is more dangerous, and why?
3. Typing 3.5 for the number of students stopped the program, even though 3.5 is obviously a number. Explain why int.Parse refused it.

Submit

Submit five things to the dropbox:

1. Your 1-9-planner program file.
2. A copy of one full run with 47 students and buses of 6.
3. The three-fundraiser number as it printed before you added :F2, and as it printed after.
4. Your five Task 4 results, with the line numbers.
5. Your three reflection answers.

Activity Complete