1.1 Zoo Learning Activity

Overview

Object Instantiation and Assigning Field Values

In this activity, you will start from the provided Zoo 1.1 LastName project and complete the first version of the Como Zoo object model.

User Story: Como Zoo Starter Program

The manager of Como Zoo has asked for the first version of a program that stores basic zoo information. This version will create the main Como Zoo object and connect it to the first objects the zoo needs to track: a featured animal, restrooms, a ticket booth, and the employee working at the booth.

This checkpoint gives the rest of the project a foundation. Later checkpoints will build on these objects and add more behavior.

Acceptance Criteria

Create a ComoZoo object.
Store the zoo's name and capacity.
Store a featured animal with its starting information.
Store both a ladies' restroom and a men's restroom.
Store a ticket booth with its ticket price.
Store the employee assigned to the ticket booth.
Run the program and verify the object values with the debugger.

Task List

Set Up Zoo Starting Code
Explore the New Como Zoo Event Handler
Instantiate the Como Zoo
Assign the Como Zoo's Capacity
Create the Featured Animal
Assign the Como Zoo's Remaining Main Fields
Assign the Featured Animal's Fields
Assign the Restroom and Ticket Booth Fields
Assign the Attendant's Fields
Finish and Submit
Review the Checkpoint Summary

Exact Casing Matters

Names in C# must match exactly. A missing capital letter, a renamed event handler that does not match XAML, or a changed class or field name can prevent the project from building or running correctly.

Watch Out For

Most issues in this checkpoint come from one character being different: a missing capital letter, a renamed event handler that does not match XAML, or a class file that was created outside the expected folder.

Before You Begin

Each code block shows only the line or lines you need to add or change. Do not recopy code that is already in the file. Place each snippet inside the correct method and inside the correct set of braces.

For this checkpoint, the code changes belong in ZooScenario/MainWindow.xaml.cs, inside the newComoZooButton_Click event handler.

You have some freedom in how you organize the lines. The key rule is that an object must exist before you assign values to its fields.

Set Up Zoo Starting Code

Begin with the starter ZIP file supplied by your instructor.
Related Pages
Need a Refresher?
Review these previously introduced topics if you need help:
- Opening Visual Studio
- Opening Solutions in Visual Studio
1. Download Zoo 1.1 LastName.zip from this folder.
2. Unzip the folder into your working location.
3. Rename the parent folder and solution name by replacing LastName with your own last name, if your instructor requires that naming pattern.
4. Open the solution in Visual Studio.
5. If Visual Studio prompts you to restore packages, restore the NuGet packages before you start editing.
Rename the extracted project folder by replacing LastName with your own last name.
Rename the solution file by replacing LastName with your own last name.
Open the solution and confirm that the solution and project names use the required naming pattern.
If prompted, restore the NuGet packages and wait for the restore to finish.
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Explore the New Como Zoo Event Handler
The Goal
Before adding any zoo code, confirm that the New Como Zoo button is already connected to code that runs when the button is clicked.
Your Task
Open ZooScenario/MainWindow.xaml, locate the New Como Zoo button, and double-click it. Visual Studio should open MainWindow.xaml.cs and place the cursor inside the existing newComoZooButton_Click event handler.
Related Pages
- Debugging Fundamentals
Double-clicking the button opens its event handler in MainWindow.xaml.cs.
What Is an Event Handler?
An event handler is a method that runs when something happens in the application. Here, clicking the New Como Zoo button causes Visual Studio to call newComoZooButton_Click. The method can be empty and still run when the button is clicked.
Need a Refresher?
Review these previously introduced topics if you need help:
- Running and Stopping Applications in Visual Studio
- Setting Breakpoints in Visual Studio
Verify Your Work
1. Open ZooScenario/MainWindow.xaml, locate the New Como Zoo button, and double-click it.
2. Confirm that Visual Studio opens ZooScenario/MainWindow.xaml.cs and places the cursor inside newComoZooButton_Click.
3. Click in the gray margin to the left of a line inside the empty event handler. A red breakpoint dot should appear. You can also press F9 to toggle a breakpoint on the current line.
4. Press F5 (Start Debugging) to run the application.
5. Click the New Como Zoo button and verify that Visual Studio stops at the breakpoint, even though the event handler does not contain any zoo code yet.
6. Press F5 (Continue) to continue running the application.
7. Stop debugging, then choose Debug > Delete All Breakpoints. You can also press Ctrl+Shift+F9 to remove all breakpoints.
8. Run the application again with F5, click the New Como Zoo button, and confirm that the application continues running without stopping in Visual Studio.
What This Means
The button is already connected to its event handler. A breakpoint pauses the program so you can inspect what is happening, but the breakpoint is not required for the button or the event handler to work.
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Instantiate the Como Zoo
Related Pages
The Goal

The MainWindow already has a ComoZoo field, but that field does not point to a real Zoo object yet.

Your Task

Inside the newComoZooButton_Click event handler, create one new Zoo object and store it in this.ComoZoo. Place it near the start of the method, before any code that uses this.ComoZoo.
Reading the Diagram
Diagram markers show what was added during the current task. Use the Options menu to switch between the color marker and the lettered accessible marker.
- New: Added during the current task.
Current object state after this task.
```
// Create an instance of the Zoo class.
this.ComoZoo = new Zoo();
```
What This Code Does

This line creates one Zoo object in memory. The this.ComoZoo = part saves a reference to that object so the rest of the method can keep filling in information for the same zoo. The comment above the line labels this part of the event handler so the object-creation code is easy to distinguish from the field assignments that follow.

Show where the student should add the Zoo object instantiation inside MainWindow.xaml.cs.
Show the breakpoint and the Locals or Watch window after F10 (Step Over), with this.ComoZoo no longer null.
Need a Refresher?
Review these previously introduced topics if you need help:
- Stepping Over Code (F10 Key)
- Using the Visual Studio Autos Window
Verify Your Work
1. Open ZooScenario/MainWindow.xaml.cs.
2. Inside the newComoZooButton_Click event handler, set a breakpoint on this.ComoZoo = new Zoo();.
3. Start the application by pressing F5 (Start Debugging) or selecting Debug > Start Debugging.
4. Click the New Como Zoo button.
5. Verify that Visual Studio stops on the breakpoint.
6. Press F10 (Step Over) to execute the line, then use the Locals or Watch window to verify that this.ComoZoo is no longer null.
7. Press F5 (Continue) to continue running the application, then stop debugging before moving on.
What This Means

Once this line runs, this.ComoZoo is no longer null. It now points to the zoo object that the rest of this checkpoint will fill in.

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Assign the Como Zoo's Capacity
Related Pages
The Goal

The zoo object now exists, but its Capacity field still has its default value.

Your Task

Give the existing zoo object a capacity value. Add this after this.ComoZoo has been created, near the other zoo field assignments.

Current object state after this task.
```
// Assign field values of Como Zoo.
this.ComoZoo.Capacity = 1000;
```
Understanding the Change

This line does not create another object. It follows the reference stored in this.ComoZoo and fills in the Capacity field on the existing zoo object.

Show this.ComoZoo.Capacity in the Locals or Watch window after the assignment executes.
Need a Refresher?
Review these previously introduced topics if you need help:
- Assigning values to fields
Verify Your Work
1. Open ZooScenario/MainWindow.xaml.cs.
2. Inside newComoZooButton_Click, set a breakpoint on this.ComoZoo.Capacity = 1000;.
3. Start the application with F5 (Start Debugging).
4. Click the New Como Zoo button.
5. When the breakpoint is reached, inspect this.ComoZoo.Capacity. It should still show its previous/default value before the line executes.
6. Press F10 (Step Over) to execute the capacity assignment.
7. Inspect this.ComoZoo.Capacity again and verify that it now contains 1000.
Try the Error Intentionally
Why You Are Trying This
Before moving on, intentionally create a common programming mistake so you can see why the order of these statements matters. The line this.ComoZoo = new Zoo(); must run before the capacity assignment. Otherwise, this.ComoZoo is still null, and the program cannot assign a capacity to a zoo object that does not exist.
You will temporarily comment out the object-creation line to observe the error. Restore the line before continuing to the next task.
and Diagnosing a ReferenceException.
1. Stop debugging and place // at the beginning of this.ComoZoo = new Zoo(); so that line is temporarily commented out.
2. Set a breakpoint on this.ComoZoo.Capacity = 1000; in ZooScenario/MainWindow.xaml.cs.
3. Start the application with F5 and click the New Como Zoo button.
4. When execution reaches the capacity line, inspect this.ComoZoo and confirm that it is null.
5. Press F10 (Step Over). Observe the null-reference error because the program tried to use a Zoo object that was never created.
6. Stop debugging and remove the // from this.ComoZoo = new Zoo();.
7. Run the application again and confirm that the capacity assignment now executes successfully.
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Create the Featured Animal

The Goal

Como Zoo needs an animal to showcase, but the zoo does not have an Animal object assigned yet.

Your Task

Create one Animal object and store it in the zoo's FeaturedAnimal field. Add this after this.ComoZoo exists. It may be grouped with the other object-creation lines.
Related Pages
- Assigning Objects
- Understanding Object State
Current object state after this task.
```
// Create the featured animal.
this.ComoZoo.FeaturedAnimal = new Animal();
```
What This Code Does

This gives the zoo a reference to an animal object. Later, when you write this.ComoZoo.FeaturedAnimal.Age, the program starts with the zoo, follows its FeaturedAnimal reference, and then fills in that animal's age.

Show the FeaturedAnimal instantiation line in the event handler.
Show this.ComoZoo.FeaturedAnimal changing from null to an Animal object after F10 (Step Over).
Verify Your Work
1. Open ZooScenario/MainWindow.xaml.cs.
2. Inside newComoZooButton_Click, set a breakpoint on this.ComoZoo.FeaturedAnimal = new Animal();.
3. Start the application with F5 (Start Debugging).
4. Click the New Como Zoo button.
5. When the breakpoint is reached, inspect this.ComoZoo.FeaturedAnimal. It should be null before the line executes.
6. Press F10 (Step Over) to execute the line.
7. Inspect this.ComoZoo.FeaturedAnimal again and verify that it changed from null to an Animal object.
What You Accomplished

The zoo now has a featured animal object. The next lines will not create another animal; they will fill in fields on the animal object you just assigned.

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Assign the Como Zoo's Remaining Main Fields

The Goal

The zoo object still needs its main related objects and its name.

Your Task

Create the restroom and ticket booth objects, and assign the zoo's name. Add these lines after the zoo object exists. The restroom and booth objects must be created before you assign values to their fields later.
Related Pages
- Referencing Nested Objects
Focused Diagram
To keep larger diagrams readable, previously completed details may be folded into [...]. The object still exists; only its unrelated details are hidden so you can focus on the current task.
Current object state after this task.
Think About Code Organization
The Name assignment appears in this task because this is where you are adding the zoo's remaining information. The code will work here because this.ComoZoo has already been created.
However, Name and Capacity are both direct field values of the same Zoo object. Grouping related field assignments together often makes the program easier to read, debug, and maintain.
You may leave this.ComoZoo.Name = "Como Zoo"; in this section, or move it so it appears beside this.ComoZoo.Capacity = 1000;. Both placements are valid. The important ideas are that the Zoo object is created first and that related assignments are organized in a way that clearly shows the program's flow.
```
// Create the restrooms.
this.ComoZoo.LadiesRoom = new Restroom();
this.ComoZoo.MensRoom = new Restroom();
// Assign the remaining field value of Como Zoo.
// You may place this beside Capacity to group Zoo field values.
this.ComoZoo.Name = "Como Zoo";
// Create the ticket booth.
this.ComoZoo.TicketBooth = new Booth();
```
Understanding the Change

The restroom and ticket booth lines create objects. The name line fills in a string value on the zoo object.

Show LadiesRoom, MensRoom, TicketBooth, and Name under this.ComoZoo in the debugger.
Verify Your Work
1. Open ZooScenario/MainWindow.xaml.cs.
2. Inside newComoZooButton_Click, set a breakpoint on the first line in this group, such as this.ComoZoo.LadiesRoom = new Restroom();.
3. Start the application with F5 (Start Debugging) and click the New Como Zoo button.
4. Press F10 (Step Over) several times to execute the remaining main field assignments one line at a time.
5. As you step, verify that this.ComoZoo.LadiesRoom, this.ComoZoo.MensRoom, and this.ComoZoo.TicketBooth change from null to objects.
6. Also verify that this.ComoZoo.Name becomes "Como Zoo".
What's Different Now?

The main zoo object now has references to its restroom objects and ticket booth object. It also has a name stored directly on the zoo.

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Assign the Featured Animal's Fields

The Goal

The animal object exists, but it does not yet have any details.

Your Task

Fill in the fields on the existing FeaturedAnimal object. Add these lines after FeaturedAnimal has been assigned a new Animal object.
Related Pages
- Object References in UML
- Fields in UML
Current object state after this task.
```
// Assign field values of the featured animal.
this.ComoZoo.FeaturedAnimal.Age = 4;
this.ComoZoo.FeaturedAnimal.Gender = "Female";
this.ComoZoo.FeaturedAnimal.IsPregnant = true;
this.ComoZoo.FeaturedAnimal.Name = "Dolly";
this.ComoZoo.FeaturedAnimal.Type = "Dingo";
this.ComoZoo.FeaturedAnimal.Weight = 35.3;
```
Show the expanded FeaturedAnimal object with Name, Type, Gender, Age, Pregnant, and Weight.
Verify Your Work
1. Open ZooScenario/MainWindow.xaml.cs.
2. Inside newComoZooButton_Click, set a breakpoint on the first featured animal field assignment, such as this.ComoZoo.FeaturedAnimal.Age = 4;.
3. Start the application with F5 (Start Debugging) and click the New Como Zoo button.
4. Press F10 (Step Over) several times to execute the featured animal field assignments one line at a time.
5. Inspect this.ComoZoo.FeaturedAnimal and verify that its fields contain Dolly, Dingo, Female, age 4, pregnant set to true, and weight 35.3.
Take a Closer Look

Each line starts at the window, follows the ComoZoo reference, follows the FeaturedAnimal reference, and then fills in one field on that animal.

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Assign the Restroom and Ticket Booth Fields

The Goal

The restroom and ticket booth objects exist, but they still need values. The ticket booth also needs an employee object before you can fill in employee information.

Your Task

Fill in the restroom fields, set the ticket price, and create the attendant object. Add these lines after LadiesRoom, MensRoom, and TicketBooth have been created.
Related Pages
- Object Lifecycle
Current object state after this task.
```
// Assign field values of the ladies' restroom.
this.ComoZoo.LadiesRoom.Capacity = 4;
this.ComoZoo.LadiesRoom.Gender = "Female";
// Assign field values of the men's restroom.
this.ComoZoo.MensRoom.Capacity = 4;
this.ComoZoo.MensRoom.Gender = "Male";
// Create and assign field values of the ticket booth.
this.ComoZoo.TicketBooth.Attendant = new Employee();
this.ComoZoo.TicketBooth.TicketPrice = 15.00m;
```
What This Code Does

The ticket booth can store a reference to an employee. The line with new Employee() creates that employee object so the next section can fill in the attendant's name and number.

Show the expanded restroom and ticket booth objects with their assigned values.
Verify Your Work
1. Open ZooScenario/MainWindow.xaml.cs.
2. Inside newComoZooButton_Click, set a breakpoint on the first restroom field assignment, such as this.ComoZoo.LadiesRoom.Capacity = 4;.
3. Start the application with F5 (Start Debugging) and click the New Como Zoo button.
4. Press F10 (Step Over) several times to execute the restroom and ticket booth assignments one line at a time.
5. Inspect this.ComoZoo.LadiesRoom and this.ComoZoo.MensRoom to confirm that each has a capacity and gender value.
6. Inspect this.ComoZoo.TicketBooth to confirm that TicketPrice is 15.00 and Attendant is no longer null.
Putting It Together

The zoo now has restroom details and a ticket booth that knows its ticket price. The booth also has an attendant object ready for employee information.

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Assign the Attendant's Fields

The Goal

The ticket booth now has an attendant object, but the attendant does not yet have values.

Your Task

Fill in the fields on the existing attendant object. Add these lines after the attendant object has been created.

Current object state after this task.
```
// Assign field values of the ticket booth attendant.
this.ComoZoo.TicketBooth.Attendant.Name = "Sam";
this.ComoZoo.TicketBooth.Attendant.Number = 42;
```
Show the expanded Attendant object with the expected Name and Number.
Verify Your Work
1. Open ZooScenario/MainWindow.xaml.cs.
2. Inside newComoZooButton_Click, set a breakpoint on this.ComoZoo.TicketBooth.Attendant.Name = "Sam";.
3. Start the application with F5 (Start Debugging) and click the New Como Zoo button.
4. Press F10 (Step Over) to execute the attendant name and number assignments one line at a time.
5. Inspect this.ComoZoo.TicketBooth.Attendant and verify that the name is "Sam" and the number is 42.
Key Takeaway

The ticket booth attendant now has identifying information. The program can connect the ticket booth to a specific employee instead of leaving the employee object blank.

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Finish and Submit

Before submitting, make sure the project runs and uses the expected object values.
Related Pages
- Diagnosing StyleCop Errors
StyleCop Must Be Clean
StyleCop is active for this project. Before submitting, build the solution and resolve every StyleCop warning introduced by your changes. The guided comments in this walkthrough are complete sentences and end with periods so they follow the expected comment style.
Need a Refresher?
Review these previously introduced topics if you need help:
- Using IntelliSense
Verify Your Work
1. Open ZooScenario/MainWindow.xaml.cs.
2. Inside newComoZooButton_Click, set a breakpoint on this.ComoZoo = new Zoo();.
3. Start the application with F5 (Start Debugging).
4. Click the New Como Zoo button.
5. Press F10 (Step Over) to execute the method one line at a time and inspect this.ComoZoo, FeaturedAnimal, LadiesRoom, MensRoom, TicketBooth, and Attendant.
6. Confirm that each object exists and that the values match the checkpoint requirements.
7. Press F5 (Continue) to continue running and confirm that the application does not stop on an exception.
8. Build the solution by selecting Build > Build Solution.
9. Open the Error List and review both errors and warnings.
10. Resolve every StyleCop warning caused by your work before submitting.
11. Build the solution again and confirm that no new errors or StyleCop warnings remain.
12. Stop debugging, save your work, and submit according to your instructor's directions.
Submit Your Work
Stop debugging, save your work, and submit according to your instructor's directions.
Feedback System
Need a Refresher?
Review these pages if you need help using the Feedback System.
- Signing Up for the Feedback System
- Submitting Code
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Checkpoint Summary

You created the first complete Como Zoo object graph. The final diagram shows the objects, references, and field values that should exist when the checkpoint is complete.

A Zoo object is assigned to MainWindow.ComoZoo.
The Zoo stores its name and capacity.
The Zoo references a featured animal, two restrooms, and a ticket booth.
The ticket booth references its attendant.

Diagram MarkerNew in this checkpoint

Ending object diagram. All objects, reference names, and field values added during Zoo 1.1 are marked with green squares. — Ending object diagram for Zoo 1.1.

1.1 Zoo Learning Activity

Overview

Object Instantiation and Assigning Field Values

User Story: Como Zoo Starter Program

Acceptance Criteria

Task List

Set Up Zoo Starting Code

Explore the New Como Zoo Event Handler

The Goal

Your Task

Verify Your Work

Instantiate the Como Zoo

The Goal

Your Task

Verify Your Work

Assign the Como Zoo's Capacity

The Goal

Your Task

Verify Your Work

Try the Error Intentionally

Create the Featured Animal

The Goal

Your Task

Verify Your Work

Assign the Como Zoo's Remaining Main Fields

The Goal

Your Task

Verify Your Work

Assign the Featured Animal's Fields

The Goal

Your Task

Verify Your Work

Assign the Restroom and Ticket Booth Fields

The Goal

Your Task

Verify Your Work

Assign the Attendant's Fields

The Goal

Your Task

Verify Your Work

Finish and Submit

Verify Your Work

Submit Your Work

Checkpoint Summary