Lesson 46 - Working with the List Collection

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

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In this lesson, we're going to talk about working with Collections, specifically the kind that holds generic types. Collections perform the same type of function in code that arrays do, but tend to be easier to work with. This is because Collections are strongly typed – meaning they enforce a very specific class type to be entered – and easily allow for elements to be added or removed. This lesson will primarily look at the List Collection, which is generic (as indicated by the angled brackets):


A List is a type, within the .NET Framework, that can store multiple items (just like an array) of a single type determined within angled brackets. The <T> part refers to the class definition for List, that can take in any type and then wherever T is referenced throughout the class, it assumes the type given.


The <T> within the angled brackets means that the list is currently generic, capable of taking in any type. What makes Lists stand out, though, is the ability to determine what the type is by providing it within the angled brackets, such as in these examples:



You can make any class or method generic by postfixing <T> after the identifier. The topic of Generics is somewhat advanced, but you will see one of its greatest purposes by using Lists and Dictionaries. Keep in mind that “generic” refers to the class/method definition side of the equation. In actuality, the type handled by a generic class/method becomes specific as soon as you make use of it (through an instance, or calling a method, for example).

Step 1: Create a New Project

Create a new ASP.NET project for this lesson and call it “CS-ASP_046” and include a single resultLabel Control:


Also, add a Car class, and within it write the following:


In the Default.aspx.cs, let’s create several instances of a Car object:


Step 2: Make A List<Car> and Add Cars To It

And now let’s make a List of type Car and add each car to the List using the Add() helper method available to the List instance. Note that once the generic type becomes specific (in this case, of type Car), you can only add cars to the List:


Since a List is much like an array, you can do many of the same things you’ve come to expect from arrays:



Step 3: Previewing the Power of Lambda Expressions

One of the most useful features of Collections in general is their built-in methods that utilize Lambda Expressions. While outside of the scope of this lesson, a Lambda Expression could be thought of as a compact method that you can define and insert into the input argument of another method. To give you a sense of the simplicity and power of Lambda Expressions we’ll briefly look here at some typical usage scenarios. While the mechanics of how this all works is founded upon more advanced topics, such as Generic Delegates and Anonymous Methods, what should be clear is how Collections allow for all kinds of data manipulation and retrieval at the hands of very little code.

Here a Lambda Expression is used in the FindAll() method to retrieve a List<Car> of all elements in cars that match “White” for the Color field (if you wanted to find cars of a different color, simply change the match string to a different color):


Another common scenario is to change values for a particular field of each element in the List. You can do that by accessing the ForEach() method and passing in the following Lambda Expression – in this case applying a new coat of paint to each car in the List:


If you want to filter the List by cars made within a certain year, you can do so with the Exists() method. And since it returns a bool – depending on if a match is found with the Lambda Expression input argument – we can wrap it in a conditional as follows:


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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