C# - Switch Statement

C# switch case statement is a control flow structure that allows us to execute distinct blocks of code depending on the value of a variable by comparing it against numerous possible case values.

We can say that it 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

Following is the syntax of the c# switch statement −

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);
}

Rules for Using switch Statement

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.

Flow Diagram

Example: Understanding Switch Statement

Here, in this c# program, we construct a code that demonstrates the use of a switch statement −

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();
      }
   }
}

Output

When the above code is compiled and executed, it produces the following result −

Well done
Your grade is B

Example: Display Week Day

In this example, we use the switch case statement to display the weekday if the integer value is given −

using System;
public class Example {
   public static void Main() {
      int day = 5; 
      switch (day)
      {
         case 1:
            Console.WriteLine("Sunday");
            break;
         case 2:
            Console.WriteLine("Monday");
            break;
         case 3:
            Console.WriteLine("Tuesday");
            break;
         case 4:
            Console.WriteLine("Wednesday");
            break;
         case 5:
             Console.WriteLine("Thursday");
             break;
         case 6:
            Console.WriteLine("Friday");
            break;
         case 7:
            Console.WriteLine("Saturday");
            break;
         default:
            Console.WriteLine("Invalid input! Please enter a number between 1 and 7.");
            break;
      }
   }
}

Output

Following is the output −

Thursday