Architect Arithmetic Errors from the Switch Statement

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I keep getting cannot convert void to bool errors from the Switch statments.
What am I doing wrong?

using System;

namespace ArchitectArithmetic
{
class Program
{
public static void Main(string args)
{
Console.WriteLine(“Hello, there! What monument would you like to work with? Please choose from one of the following: Teotihuacan, TajMahal, Mecca”);
string monument = Console.ReadLine();

  switch(monument)
  {
    case "Teotihuacan":
      Console.WriteLine(CalculateTotalTeoCost());
      break;
    case "TajMahal":
      Console.WriteLine(CalculateTotalTajCost());
      break;
    case "Mecca": 
      Console.WriteLine(CalculateTotalMeccaCost());
      break;
    default: 
      Console.WriteLine("It is important that you improve your reading skills.  Please choose from one of the following: Teotihuacan, TajMahal, Mecca");

  }

}

public static double RectArea(double length, double width)
{
  return length * width;
}
public static double CircleArea(double radius)
{
  return Math.PI * Math.Pow(radius, 2);
}

public static double TriangleArea(double bottom, double height)
{
  return 0.5 * bottom * height;
}

public static void CalculateTotalTeoCost()
{
  double teoRect = RectArea(1500, 2500);
  double teoCircle = CircleArea(375) * 0.5; 
  double teoTri = TriangleArea(500, 750);
  double totalCost = Math.Round((teoRect + teoCircle + teoTri) * 180, 2);

  Console.WriteLine($"Total construction of Teotihuacan is {totalCost} pesos.");
}

public static void CalculateTotalTajCost()
{
double tajRect = RectArea(90.5, 90.5);
double tajTri = TriangleArea(24, 24);
double tajTotal = tajRect - (4 * tajTri);

  double totalCost = Math.Round(tajRect * 180, 2);

  Console.WriteLine($"Total construction of Taj Mahal in Agra, India is {totalCost}.");
}

public static void CalculateTotalMeccaCost()
{
double meccaBigRect = RectArea(284, 264);
double meccaSmallRect = RectArea(180, 106);
double meccaTri = TriangleArea(84, 264);
double totalCost = Math.Round((meccaBigRect + meccaSmallRect - meccaTri) * 180, 2);

  Console.WriteLine($"Total construction of Great Mosque of Mecca in Mecca, Saudi Arabia is {totalCost}.");
}

}
}

1 Like
2

For proper formatting of code in forum posts, see the thread:

In your switch statement, you have:

Console.WriteLine(CalculateTotalTeoCost());

The above statement makes a call to the method CalculateTotalTeoCost and then tries to pass the returned (returned by CalculateTotalTeoCost) value as an argument to the Console.WriteLine method. But, in the code you have posted CalculateTotalTeoCost doesn’t return any value because the return type is void in the method declaration:

public static void CalculateTotalTeoCost() {...

void specifies that a method doesn’t return a value (see documentation for void). This causes a problem because the WriteLine method is expecting a value to be passed as the argument in the statement Console.WriteLine(CalculateTotalTeoCost());

How you solve this issue depends on how you want your program to behave.

  • One way is to leave CalculateTotalTeoCost as it is and instead modify the statements in the switch:
switch(monument) {
    case "Teotihuacan":
        // Console.WriteLine(CalculateTotalTeoCost()); Delete this statement
        CalculateTotalTeoCost();
        break;
     case ...
}
 
public static void CalculateTotalTeoCost() {
  // ...
  Console.WriteLine($"Total construction of Teotihuacan is {totalCost} pesos.");
}

In this version, if the switch case matches, then the CalculateTotalTeoCost method is called and printing the output is left to the CalculateTotalTeoCost method.

  • Another possible solution is to the leave the switch statements unchanged, but modify the CalculateTotalTeoCost method so that the method returns a string instead of printing the output:
switch(monument) {
    case "Teotihuacan":
        Console.WriteLine(CalculateTotalTeoCost());
        break;
     case ...
}
 
public static string CalculateTotalTeoCost() {
  // ...
  return $"Total construction of Teotihuacan is {totalCost} pesos.";
}

In this version, CalculateTotalTeoCost returns a string. Writing this returned sting to the console is left as the job of the switch statement.

Remarks:

  • You will need to make similar changes by EITHER deleting/editing all the Console.WriteLine statements from all the other cases as well OR modifying the return types of all the methods CalculateTotalTeoCost, CalculateTotalTajCost and CalculateTotalMeccaCost

  • Also, you will need to add the break; statement after the default case as well. In C/C++ and many other languages, the break would not be necessary if the default case is at the bottom of the switch statement. But in C#, you will get an error similar to:

Control cannot fall out of switch from final case label (‘default:’)

because in C#, you must explicitly transfer control (break, return, goto, throw).
break; isn’t necessary per se, rather the reason is: Four switch oddities [See the explanation for the second oddity titled “Case 2” in this link)

It requires that every switch section, including the last one , have an unreachable end point