Lesson 54 - Understanding the switch() Statement

Tutorial Series: Free C# Fundamentals via ASP.NET Web Apps

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This lesson will discuss the switch() statement, which is a flow control similar to an if() statement. An apt analogy is that of a switching railroad track that changes course depending on a certain condition being met. The main difference between a switch() and an if() is the former evaluates a single operand against a selection of case scenarios, whereas an if() can have a cascade of varying evaluations each using multiple operands. In both conditional statements, different blocks of code will execute depending on if an evaluation match is found.

Step 1: Create a New Project

For this lesson, create a new ASP.NET project called “CS-ASP_054” with a single resultLabel Control:


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You can access the switch() code snippet by typing in “switch” and hitting the tab key twice:


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Step 2: Understanding What a switch() Consists Of

A switch() statement typically consists of:

  1. A single operand to be evaluated.

  2. Conditions (cases) evaluated against that operand.

  3. A default action if none of the conditions evaluate True.


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Step 3: Understanding ‘case’, ‘default’ and ‘break’ Components

The above example would display “Default (Optional)” because none of the cases, 0 or 1, match the actual value of the operand being evaluated, 4. However, if a case does match the value of the evaluated element you will see the “code block” execute for the particular case:


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The break keyword tells the compiler to exit – or break out of – the switch() statement after the code block has completed. If you do not use a break after a case, it groups it with the next case in line. This could be read as saying “if the case is 0 or 1, perform the code block for case 1)


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Tip:

You can also use the return keyword, which would exit the switch() statement entirely, as well as exiting the method it is operating within:


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It’s important to realize that returning out of the method happens right away, meaning that any code occurring below that keyword will never execute:


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Step 4: Using the ‘goto’ Keyword

You can use the goto keyword to execute a code block associated with another case. In this scenario, if case 2 is a match it will add “Case 2” to result and then immediately go to case 99 and break out of the switch() entirely:


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To make this a bit more obvious, change the following case and run the application:


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You can even perform a mathematical calculation and return the result as the matching case. This is equivalent to writing “case 2”:


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You can also use the switch() to perform exception handling:


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Step 5: Pairing switch() with Enum

Switch() statements work particularly well with enums, and there are even some handy shortcuts built into Visual Studio to facilitate this. To demonstrate this, let’s re-create the Character class and CharacterType enum from the previous lesson:


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In Page_Load() type in the following code, using the code-snippet shortcut for the switch() statement:


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After you type in the hero.Type property hit the Enter key on your keyboard twice, and Visual Studio will extrapolate the available values for the enum as cases within the switch():


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All you have to do now is add your case specific code blocks, and you have a switch() and enum working in tandem. The general rule of thumb is to use switch() statements when evaluating possible values in enums and you need to check a variety of case scenarios against a single operand, otherwise use a switch() wherever it produces a more elegant solution to what an if() statement would provide.


Related Articles in this Tutorial:

Lesson 1 - Series Introduction

Lesson 2 - Installing Visual Studio 2015

Lesson 3 - Building Your First Web App

Lesson 4 - Understanding What You Just Did

Lesson 5 - Working with Projects in Visual Studio

Lesson 6 - Simple Web Page Formatting in Visual Studio

Challenge 1

Solution 1

Lesson 7 - Variables and Data Types

Lesson 8 - Data Type Conversion

Lesson 9 - Arithmetic Operators

Lesson 10 - C# Syntax Basics

Challenge 2 - ChallengeSimpleCalculator

Solution - ChallengeSimpleCalculator

Lesson 11 - Conditional If Statements

Lesson 12 - The Conditional Ternary Operator

Challenge 3 - ChallengeConditionalRadioButton

Solution - Challenge Conditional RadioButton

Lesson 13 - Comparison and Logical Operators

Lesson 13 Challenge - First Papa Bob's Website

Solution - Challenge First Papa Bob's Website

Lesson 14 - Working with Dates and Times

Lesson 15 - Working With Spans of Time

Lesson 16 - Working with the Calendar Server Control

Challenge 4 - Challenge Days Between Dates

Solution - Challenge Days Between Dates

Lesson 17 - Page_Load and Page.IsPostBack

Lesson 18 - Setting a Break Point and Debugging

Lesson 19 - Formatting Strings

Challenge 5 - Challenge Epic Spies Assignment

Solution - Challenge Epic Spies Assignment

Lesson 20 - Maintaining State with ViewState

Lesson 21 - Storing Values in Arrays

Lesson 22 - Understanding Multidimensional Arrays

Lesson 23 - Changing the Length of an Array

Challenge 6 - Challenge Epic Spies Asset Tracker

Solution - Challenge Epic Spies Asset Tracker

Lesson 24 - Understanding Variable Scope

Lesson 25 - Code Blocks and Nested If Statements

Lesson 26 - Looping with the For Iteration Statement

Challenge 7 - Challenge For Xmen Battle Count

Solution - Challenge For Xmen Battle Count

Lesson 27 - Looping with the while() & do...while() Iteration Statements

Lesson 28 - Creating and Calling Simple Helper Methods

Lesson 29 - Creating Methods with Input Parameters

Lesson 30 - Returning Values from Methods

Lesson 31 - Creating Overloaded Methods

Lesson 32 - Creating Optional Parameters

Lesson 33 - Creating Names Parameters

Lesson 34 - Creating Methods with Output Parameters

Challenge 8 - Challenge Postal Calculator Helper Methods

Solution - Challenge Postal Calculator Helper Methods

Mega Challenge Casino

Solution - Mega Challenge Casino

Lesson 35 - Manipulating Strings

Challenge 9 - Phun With Strings

Solution - Challenge Phun With Strings

Lesson 36 - Introduction to Classes and Objects

Challenge - Hero Monster Classes Part 1

Solution - Hero Monster Classes Part 1

Challenge - Hero Monster Classes Part 2

Solution - Challenge Hero Monster Classes Part 2

Lesson 37 - Creating Class Files Creating Cohesive Classes and Code Navigation

Lesson 38 - Understanding Object References and Object Lifetime

Lesson 39 - Understanding the .NET Framework and Compilation

Lesson 40 - Namespaces and Using Directives

Lesson 41 - Creating Class Libraries and Adding References to Assemblies

Lesson 42 - Accessibility Modifiers, Fields and Properties

Lesson 43 - Creating Constructor Methods

Lesson 44 - Naming Conventions for Identifiers

Lesson 45 - Static vs Instance Members

Challenge 10 - Challenge Simple Darts

Solution - Challenge Simple Darts

Lesson 46 - Working with the List Collection

Lesson 47 - Object Initializers

Lesson 48 - Collection Initializers

Lesson 49 - Working with the Dictionary Collection

Lesson 50 - Looping with the foreach Iteration Statement

Lesson 51 - Implicitly-Typed Variables with the var Keyword

Challenge 11 - Challenge Student Courses

Solution - Challenge Student Courses

Mega Challenge War

Solution - Mega Challenge War

Lesson 52 - Creating GUIDs

Lesson 53 - Working with Enumerations

Lesson 54 - Understanding the switch() Statement

Lesson 55 - First Pass at the Separation of Concerns Principle

Lesson 56 - Understanding Exception Handling

Lesson 57 - Understanding Global Exception Handling

Lesson 58 - Understanding Custom Exceptions

Lesson 59 - Creating a Database in Visual Studio

Lesson 60 - Creating an Entity Data Model

Lesson 61 - Displaying the DbSet Result in an ASP.NET GridView

Lesson 62 - Implementing a Button Command in a GridView

Lesson 63 - Using a Tools-Centric Approach to Building a Database Application

Lesson 64 - Using a Maintenance-Driven Approach to Building a Database Application

Lesson 65 - Creating a New Instance of an Entity and Persisting it to the Database

Lesson 66 - Package Management with NuGet

Lesson 67 - NuGet No-Commit Workflow

Lesson 68 - Introduction the Twitter Bootstrap CSS Framework

Lesson 69 - Mapping Enum Types to Entity Properties in the Framework Designer

Lesson 70 - Deploying the App to Microsoft Azure Web Services Web Apps

Papa Bob's Mega Challenge

Papa Bob's Mega Solution Part 1 - Setting up the Solution

Papa Bob's Mega Solution Part 2 - Adding an Order to the Database

Papa Bob's Mega Solution Part 3 - Passing an Order from the Presentation Layer

Papa Bob's Mega Solution Part 4 - Creating the Order Form

Papa Bob's Mega Solution Part 5 - Adding Enums

Papa Bob's Mega Solution Part 6 - Creating an Order with Validation

Papa Bob's Mega Solution Part 7 - Calculating the Order Price

Papa Bob's Mega Solution Part 8 - Displaying the Price to the User

Papa Bob's Mega Solution Part 9 - Creating the Order Management Page


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