Switch - Case / Select - Case

Switch - Case / Select - Case

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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.

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

switch(expression) 
{     
case constant-expression1  :        
      statement(s);        
          break;     
case constant-expression2  :     
case constant-expression3  :        
        statement(s);        
              break;         
    /* 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, then it will raise a compile time error.

• 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.

This is how it works:

• The switch expression is evaluated once
• The value of the expression is compared with the values of each case
• If there is a match, the associated block of code is executed
• The break keyword terminates the switch and the flow of control jumps to the next line
• default case executes when none of the above cases is true.

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();        
           }     
      }  
  }

Result:  Well done  
         Your grade is B  

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