Lesson 32 - Creating Optional Parameters

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

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This is a short lesson that covers an interesting feature of methods in C# and that is the allowance of optional parameters. The “optional” part refers to whether or not the values for the parameter are supplied upon calling the method. If the programmer decides not to supply any values for the parameter, it then defaults to a value assigned in the method signature itself.

Step 1: Create a New Project**

Refer to where we left off with the previous lesson and use that as the starting-point for this one, and call the project “CS-ASP_032”. And in the existing performAttack() method modify it to include another optional input parameter:


cs-asp-032---creating-optional-parameters.001


Step 2: Using Optional Parameter’s for Default Values

Notice how this input parameter includes a value already assigned to it, determined before the method is even called. Also, notice that our existing calls to this method still work even though they are missing this input parameter. This is because the optional parameter we created defaults to the value if no other is given when the method is called. The other (non-optional) parameters are absolutely required and the compiler would make sure you include them otherwise it will produce an error:


cs-asp-032---creating-optional-parameters.002


The way this works here is criticalHitChance automatically takes on the value defined in the method signature unless it is explicitly overridden with a different value supplied at the method call. You will be able to identify optional parameters with Intellisense, which shows them wrapped in square brackets, along with their default value:


cs-asp-032---creating-optional-parameters.003


Step 3: Overriding the Optional Parameter’s Default Value

Now here is the performAttack() method with the optional parameter designated at the method call:


cs-asp-032---creating-optional-parameters.004


You can add as many optional parameters as you want but they must be appended after the non-optional input parameters:


cs-asp-032---creating-optional-parameters.005


cs-asp-032---creating-optional-parameters.006


Step 4: Constraints When Omitting Optional Parameter Arguments

Now, let’s see what happens if we want to omit the first optional parameter at the method call:


cs-asp-032---creating-optional-parameters.007


You will notice that the compiler doesn’t let you do this and that’s because the only parameter that is truly optional, in all cases, is the last optional parameter within the sequence. So, you can safely omit this last optional parameter, even if you choose to use the optional parameters that came before it:


cs-asp-032---creating-optional-parameters.004


Tip:

You may have noticed that we didn’t actually reference the optional parameters in the body of the performAttack() code block. Obviously you would want to make use of all of your input parameters in a real-world code project, however, this example is simply for the purpose of demonstrating how optional parameters work.


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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