Lesson 29 - Creating Methods with Input Parameters

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

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This lesson will look at how to create a method with input parameters. To illustrate this, let’s take a look at the calculateCups() helper method that we created in the previous lesson:


Although this particular solution works, it isn’t intuitively scalable if we ever want to add a new calculation – something greater than cups-to-gallons for example – as it would require a modification within the method internals (the conditional if()…else if() statements, in this case). By doing this, we increase the risk of introducing bugs into the existing code. It would be much easier if we could just pass into each call to calculateCups() the particular measurement ratio required for that calculation, and eliminating the need for the conditional block entirely.

Step 1: Add an Input Parameter to calculateCups()

This precise functionality is possible by changing the calculateCups() method so that it allows for an input parameter to be passed into the method:


By doing this, we essentially assign a variable that we can reference throughout the remaining body of this helper method, with the actual value being supplied at the method call. Now we can remove the conditional block and, in its place, incorporate the measureToCupRatio parameter in the following manner:


Step 2: Fixing Existing Calls to calculateCups()

You may have noticed that when you added the measureToCupRatio input parameter for calculateCups(), it caused all of the previous calls to calculateCups() to become decorated with a red squiggly line, indicating an error. The error simply means that you are not calling the method properly now that it requires a value to be given as an input parameter when it is called. But first, before we fix this, let’s comment out the following call as it will become problematic and require a little more effort to get working properly:


Step 3: Add the Input Parameter’s Argument at Call

Now, let’s supply all of the calculateCups() calls with values relative to its calling method’s conversion ratio (IE: 1:1 ratio between cups/cups, a 2:1 ratio between cups/pints, a 4:1 ratio between cups/quarts, and a 16:1 ratio between cups/gallons):



Notice how all of this refactoring creates the same results as before when running the application. However what has really been improved has been the maintainability and readability of the code in the backend. Not all code improvements are visible to the end-user!

Step 4: Understanding When To Use Input Parameters

The main rule of thumb for when and where to incorporate input parameters is to do so wherever you need to separate what remains the same, with what sometimes is different between each call to the helper method. In this case, what’s different each time you call the method is the measure/cup ratio, whereas the calculation details are the same with each method call. In other words, we're adding variability to the method through whatever we choose to pass in via the measureToCupRatio input parameter, while the logic within the code block remains unchanged. To demonstrate this further and to illustrate how you can utilize more than one input parameter, let’s modify the resultLabel to be more descriptive depending on which conversion was selected:


Step 5: Adding More Input Parameters

This new variable – measureName – can now be supplied, at method call, as a second input parameter:


We will now have to modify all of the calculateCups() calls with a second input parameter passed in that assumes the place wherever measureName is referenced within the method internals. Note that you could add as many input parameters as needed, separating each input parameter with a comma:


Now you can save and run the project to see the results:



Input parameters – also referred to as “arguments” when supplied at the method’s call – function in much the same way as any other variable you have come to learn about thus far. By creating an input parameter, you are essentially declaring a variable local to the method itself with its assignment being determined by whatever value is copied/passed-in at the method call. That input parameter’s variable name then becomes the identifier that we use throughout the method’s code block wherever that variable needs to be referenced.

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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