C# - Switch

The Switch statement in C# language is used to execute one of many code statements. It can be considered as group of If-else statements.

Syntax

switch (expression){
  case 1:
     statement 1;
     break;
  case 2:
     statement 2;
     break;
     ...
     ...
     ...
  case N:
     statement N;
     break;
  default:
     default statement;
     break;
}

The Switch expression is evaluated and matched with the cases. When Case matches, the following block of code is executed.

Flow Diagram:

Example:

In the example below, the switch expression is a variable called i with value 2 which is matched against case values. When the case value matches with expression value, the following block of code is executed.

using System;

class MyProgram {
  static void Main(string[] args) {
    int i = 2;
    switch(i){
      case 1: 
        Console.WriteLine("Red");
        break; 
      case 2: 
        Console.WriteLine("Blue");
        break;
      case 3: 
        Console.WriteLine("Green");
        break;
    }
  }
}

The output of the above code will be:

Blue

default and break statements

Default case and break statement are optional here.

Default Case: Default Statement is executed when there is no match between switch expression and test cases.
Break Statement: In C#, each case require break statement. With break statement, the program get out of the Switch statement after a match is found.

Example:

In the example below, the switch expression is a variable called i with value 10 which is matched against case values. As there is no case that matches with value 10, hence default block of code gets executed.

using System;
 
class MyProgram {
  static void Main(string[] args) {
    int i = 10;
    switch(i){
      case 1: 
        Console.WriteLine("Red");
        break; 
      case 2: 
        Console.WriteLine("Blue");
        break;
      case 3: 
        Console.WriteLine("Green");
        break;
      default: 
        Console.WriteLine("No match found.");
        break;
    }
  }
}

The output of the above code will be:

No match found.

Please note that, the default statement can be placed at any position in the switch statement.

Example:

Consider the example below, where default statement is placed on the top in a switch statement.

using System;
 
class MyProgram {
  static void Main(string[] args) {
    int i = 10;
    switch(i){
      default: 
        Console.WriteLine("No match found.");
        break;
      case 1: 
        Console.WriteLine("Red");
        break; 
      case 2: 
        Console.WriteLine("Blue");
        break;
      case 3: 
        Console.WriteLine("Green");
        break;
    }
  }
}

The output of the above code will be:

No match found.

Common code blocks

There are instances where same code block is required in multiple cases.

Example:

In the example below, same code block is shared for different switch cases.

using System;
 
class MyProgram {
  static void Main(string[] args) {
    int i = 10;
    switch(i){
      case 1: 
        Console.WriteLine("Red");
        break; 
      case 2:
      case 10: 
        Console.WriteLine("Blue");
        break;
      case 3: 
      case 4:
      case 5:
        Console.WriteLine("Green");
        break;
    }
  }
}

The output of the above code will be:

Blue