Question

Write a one-to-two page report on how C#'s switch statement is safer than that of C.

Answer 1

A switch statement allows a variable to be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each switch case.

Syntax

The syntax for a switch statement in C# is as follows:

switch(expression) {
   case constant-expression  :
      statement(s);
      break; /* optional */
   case constant-expression  :
      statement(s);
      break; /* optional */
  
   /* you can have any number of case statements */
   default : /* Optional */
   statement(s);
}

The following rules apply to a switch statement:

• The expression used in a switch statement must have an integral or enumerated type, or be of a class type in which the class has a single conversion function to an integral or enumerated type.

• You can have any number of case statements within a switch. Each case is followed by the value to be compared to and a colon.

• The constant-expression for a case must be the same data type as the variable in the switch, and it must be a constant or a literal.

• When the variable being switched on is equal to a case, the statements following that case will execute until a break statement is reached.

• When a break statement is reached, the switch terminates, and the flow of control jumps to the next line following the switch statement.

• Not every case needs to contain a break. If no break appears, the flow of control will fall through to subsequent cases until a break is reached.

• A switch statement can have an optional default case, which must appear at the end of the switch. The default case can be used for performing a task when none of the cases is true. No break is needed in the default case.

Flow Diagram

expression case 1 code block 1 case 2 code block 2 case 3 code block 3 default code block N

Example

using System;
namespace DecisionMaking
{
   class Program
   {
      static void Main(string[] args)
      {
         /* local variable definition */
         char grade = 'B';
         
         switch (grade)
         {
            case 'A':
               Console.WriteLine("Excellent!");
               break;
            case 'B':
            case 'C':
               Console.WriteLine("Well done");
               break;
            case 'D':
               Console.WriteLine("You passed");
               break;
            case 'F':
               Console.WriteLine("Better try again");
               break;
               default:
            Console.WriteLine("Invalid grade");
               break;
         }
         Console.WriteLine("Your grade is  {0}", grade);
         Console.ReadLine();
      }
   }
}