C# C# Basics (Retired) Perform if / else

Matthew De-Veale Cutts
Matthew De-Veale Cutts
2,115 Points

In this instance couldn't we just exempt the else statement? Why is it necessary?

while (keepGoing) {

          //Prompt the user for minutes.

          Console.Write("Enter how many minutes you exercised or type \"quit\" to exit: ");

          string entry = Console.ReadLine();

          if (entry == "quit")
          {
            keepGoing = false;
          }

              int minutes = int.Parse(entry);

              // Add Minutes to total. 

              runningTotal = runningTotal + minutes;

              // Display total minutes on screen

              Console.WriteLine("You've excercised " + runningTotal + " minutes");

              // Repeat until over.  
      }

      Console.WriteLine("Application Closing."); 

Surely with the code above, in this instance when the user enters "quit" then it would then just skip through the rest of the code all the way down to the Console.Writeline instead of attempting to run the int minutes = int.Parse(entry); etcetc. Essentially the same as if we did the code below.

using System;

namespace Treehouse.FitnessFrog { class Program { static void Main() {

      int runningTotal = 0;
      bool keepGoing = true;

      while (keepGoing) 
      {

          //Prompt the user for minutes.

          Console.Write("Enter how many minutes you exercised or type \"quit\" to exit: ");

          string entry = Console.ReadLine();

          if (entry == "quit")
          {
            keepGoing = false;
          }
          else 
          {
              int minutes = int.Parse(entry);

              // Add Minutes to total. 

              runningTotal = runningTotal + minutes;

              // Display total minutes on screen

              Console.WriteLine("You've excercised " + runningTotal + " minutes");

              // Repeat until over.  
          }
      }

      Console.WriteLine("Application Closing."); 

  }

} }

Why is it necessary for us to put the else loop in? Why is this a rule.

2 Answers

Emmanuel C
Emmanuel C
7,627 Points

In the first example, without the else, the rest of the code would still run, even if they enter quit. That keepGoing bool wouldnt be evaluated until the end of the loop when it checks the while condition and decided if it should run again.

That program should actually crash if the user enters quit, since all the if statement does is set keepGoing to false, but doesnt break out of the loop, the int.Parse would still run, and crash trying to parse "quit" into a number.

In order to not have an else statement, you can use the keyword break in that if statement, which will make the program break out of the loop, like so...

while (keepGoing) {

      //Prompt the user for minutes.
      Console.Write("Enter how many minutes you exercised or type \"quit\" to exit: ");

      string entry = Console.ReadLine();

      if (entry == "quit")
      {
           keepGoing = false;
           break;
       }

       int minutes = int.Parse(entry);

        // Add Minutes to total. 
        runningTotal = runningTotal + minutes;
        // Display total minutes on screen
        Console.WriteLine("You've excercised " + runningTotal + " minutes");
        // Repeat until over. 
}

Console.WriteLine("Application Closing."); 

Then you technically wouldnt need that bool keepGoing as a flag, since the break keyword will decide whether the loop ends or not.

Matthew De-Veale Cutts
Matthew De-Veale Cutts
2,115 Points

I see. So in these tutorials obviously we haven't learnt about break yet. So I'm kind of jumping the gun? And I just tested the first one and noticed it was crashing as a matter of fact. Should have tested it without copying haha. But basically long story cut short, you always either need an else, or a break?

Emmanuel C
Emmanuel C
7,627 Points

It does depend on the situation, for this one, the else was needed, as the user entering "quit" is suppose to end the loop. So IF the user entered a number then do appropriate calculations, but(else) if the user entered "quit" than set the keepGoing flag to false and dont do the calculation. This is very common in programming, where you would have to do different things depending on what the user enters. If statements are a great way to decide what to do depending on what they entered. If the user enter this, then do this, else if the user enters that do something else and so on.