Lesson 41 - Creating Class Libraries and Adding References to Assemblies

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

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As we saw in a previous lesson, the .NET Framework Class Library is split up across several different Assemblies, each within its own .dll file in the Framework library folder:


Assemblies are split into separate files to reduce load on resources, maximize efficiency so that we load up only what is needed to complete the task at hand, and to make code portable. This lesson will demonstrate how to create Class Libraries off of your own custom project code, and how to add references to resulting .dll Assemblies.

Step 1: Create a New Project

To begin this lesson, create an ASP.NET project called “CS-ASP_041” and in the Default.aspx add a single resultLabel:


Step 2: Add another Project to the Solution as a Class Library

For this particular Solution, we will want to add another project to it. To do this right-click on the Solution and from the menu choose:

Add > New Project…


From the list of templates select “Windows” and “Class Library,” and name the project “HeroMonster”:


And now you can access both projects within the Solution Explorer. If you want, you can even build the projects separately by right-clicking on one and choosing from the menu “Build”:


Step 3: Create Custom Classes in Class1.cs

The “HeroMonster” project will come with a default class file called “Class1.cs” and in this file we will create two separate classes called Character and Dice:


Write the following code for each class:



Step 4: Add an Outside Assembly to a Project via ‘References’

You can now add the “HeroMonster” project to the CS-ASP_041 project by right-clicking it’s “References” within the Solution Explorer:


And then selecting it under the “Projects” tab:


Step 5: Incorporating the Assembly in Code via Using Directives

Now that we have a reference to this assembly in the CS-ASP_041 project, we can add it to our class files via a using directive. Note that this directive actually loads the code library from HeroMonster, whereas the assembly reference simply allows it to be available to our project. With the directive added, you can then reference a public class, such as Character, from that library:


Step 6: Porting Over the Battle Game Code

You can now fill out Page_Load() with the code we used in the previous battle simulation game project:


We will also need to port over, into this Default class, the following helper methods:


This is an identical application to what we built before, with the difference being that we partitioned out some “Domain-specific” code – the Character and the Dice classes – factoring them out into their own Class Libraries. This is noteworthy as it allows the classes to be reused in another project, which we can also accomplish by loading the .dll created in the project’s bin folder when we ran the application.

Step 7: Adding HeroMonster.dll Assembly to a New Project

Open up a new instance of Visual Studio and create a new Project based off of a Windows Forms Application template. Even though we’re not going to deal with Windows Forms in-depth, this will demonstrate how easy it is to port over our custom Class Libraries into a different project environment, requiring very little changes:


Once the Windows Form project is open, turn to the Properties Window (F4) and simply rename the project’s Design Name to “resultLabel”:


Next, right-click on “References” underneath the main project within the Solution Explorer, and select “Add Reference”:


On the next screen you will want to click “Browse” and navigate to the folder for the project we worked on at the start of this lesson. Within that folder will be a bin folder that holds the HeroMonster.dll that was automatically built when we ran the application:


Add that .dll Assembly to the project and you will see it under “References” in the Solution Explorer:


Double-click on “Form1” in the Solution Explorer to open up the code for the Form Application:


Add the HeroMonster library as a using declaritive at the top of the script:


You can then copy all of the Page_Load(), displayResult() and printStats() code from the Default.aspx.cs in the original project – that depends on the HeroMonster class library code – and paste it into the Form1 class in the current Forms project (partially represented below, substituting Page_Load() with Form1_load() ):


If you build the project and everything is set up correctly, you should notice that there are no errors. Of course, some things will have to be changed considering that the HeroMonster code was for a Web Application and contains HTML. However, the main point here is to see how you can partition your code into individual projects, Class Libraries and .dll Assemblies in order to gain portability with the code you write.

Note that you can add references to existing Framework Assemblies using the same process. This is useful whenever you have particular functionality you want to use in your project and is already available in the Framework. To add an existing Framework Assembly, once again go to:

Solution Explorer > References > Add Reference > Assemblies > Framework

And select the Assembly relevant to your project in the right-hand pane:


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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