Exercise from Visual Studio C# 2010 fourth edition

Question

I've working on a C# application that is supposed to input miles driven and gallons used(integers) for each tankful of gas and then the application should calculate and display the miles per gallon obtained for each tankful and display combined miles per gallon obtained for all tankfuls. My issue is that the sentinel controlled aspect "-1" doesnt stop program from running, yet, the IDE kicks out a JIT debugger and I get a Microsoft.NET framework exception MileageDriven.exe[732].

Can I have some assistance, as I dont want to move beyond this exercise as future lessons build upon the last lesson. Thanks in advance. :)

using System;

public class MileagedrivenTest
{
   public static void Main(string[] args)
   {
      Mileage driverMileage = new Mileage("Driver log");

      driverMileage.DisplayMessage();
      driverMileage.DetermineMileagePerGallon();
   } // end main
} // end class MileageDrivenTest

// Fig. 1.1: MileageDriven.cs
// Mileage class that solves mileage per gallon problem
// using sentinel-controlled repetition
using System;

public class Mileage
{
   public string Gallons { get; set; }

   public Mileage (string name)
   {
      Gallons = name;
   }

   public void DisplayMessage()
   {
      Console.WriteLine("Welcome to the mileage log for\n{0}\n", Gallons);
   } // end method DisplayMessage

   //determine the average mileage for gallon per tank of gas
   public void DetermineMileagePerGallon()
   {
      int total = 0;
      int mileage; // sum of miles driven
      int gallons; // sum gallons used
      double average;

      int mileageCounter = 0;

      Console.WriteLine("Enter mileage or -1 to quit: ");
      mileage = Convert.ToInt32(Console.ReadLine());
      Console.WriteLine("Enter gallons used: ");
      gallons = Convert.ToInt32(Console.ReadLine());

      while (mileage != -1)
      {
         mileage = total + mileage;
         mileageCounter = mileageCounter + mileage;

         Console.Write("Enter next miles driven or -1 to quit: ");
         mileage = Convert.ToInt32(Console.ReadLine());         
      } // end while

      if (mileageCounter != 0)
      {
         average = (double)total / mileageCounter;

         Console.WriteLine("\nTotal of the {0} miles driven is {1} per tank is{}", mileageCounter, total);
         Console.WriteLine("Average mile per gallon is {0}", average);
      }
      else
         Console.WriteLine("No mileage entered");      
   }
}

It's hard to know how we can help without seeing either the code or the exception... — Jon Skeet, Mar 29 '12 at 07:13
indeed, I will post both the code I've written. thank you. Just one moment. — Rodney Davis, Mar 29 '12 at 07:14
Im trying to post code, no dice though. Im just learning this site. bare with me. — Rodney Davis, Mar 29 '12 at 07:18
Can you be more specific? Click "edit", paste the code, highlight it and then click on the "{}" icon. — Jon Skeet, Mar 29 '12 at 07:41
Hey Jon, finally got it edited...please dissect my creation, :) , and lend suggestions. Thank you, once again. — Rodney Davis, Mar 29 '12 at 08:07
Good morning. I want to thank you very much, seeing your interpretation of the earlier code, just tells me that I have a long way to go. Your code makes alot of sense, even though I'm still learning C#. Thank you once again. I struggled with this exercise since 8am on Tuesday. — Rodney Davis, Mar 29 '12 at 14:48

score 0 · Answer 1 · answered Mar 29 '12 at 10:13

The code you posted throws an exception on this line:

Console.WriteLine("\nTotal of the {0} miles driven is {1} per tank is{}", mileageCounter, total);

The problem is the extra {}. If you remove that the code will run but I don't think that it solves the problem that you're trying to solve. I've modified DetermineMileagePerGallon() based on my interpretation of the problem - hopefully it'll get you closer to a solution:

 //determine the average mileage for gallon per tank of gas
   public void DetermineMileagePerGallon()
   {
       int totalTankfuls = 0;
       int inputMileage;
       int totalMileage = 0; // sum of miles driven
       int totalGallons = 0; // sum gallons used

       Console.WriteLine("Enter mileage or -1 to quit: ");
       while (!Int32.TryParse(Console.ReadLine(), out inputMileage)) ;

       while (inputMileage != -1)
       {
           totalTankfuls++;

           if (inputMileage > 0)
               totalMileage += inputMileage;

           Console.WriteLine("Enter gallons used: ");
           int inputGallons;
           while (!Int32.TryParse(Console.ReadLine(), out inputGallons)) ;

           if (inputGallons > 0)
               totalGallons += inputGallons;

           Console.WriteLine("Enter mileage or -1 to quit: ");
           while (!Int32.TryParse(Console.ReadLine(), out inputMileage)) ;

       } // end while

       if (totalTankfuls > 0)
       {
           double averageMpg = (double)totalMileage / totalGallons;

           double averageMileagePerTankful = (double)totalMileage / totalTankfuls;
           Console.WriteLine("Total of {0} miles driven on {1} tanks of fuel; average is {2} miles per tankful", totalMileage, totalTankfuls, averageMileagePerTankful);
           Console.WriteLine("Average mile per gallon across all tankfuls is {0}", averageMpg);
       }
       else
           Console.WriteLine("No mileage entered");
   }

Exercise from Visual Studio C# 2010 fourth edition

1 Answers1