Errata

Several changes made to the WPF PDF posted on the book's website.

Page 500:
In the header, change "a Windows Store app page" to a "a WPF application"
The body text should be:
The Go Fish! game that you built in Chapter 8 would make a great WPF application. Open Visual Studio and create a new WPF Application project (just like you did for Save the Humans). Over the next few pages, you�ll redesign it in XAML, with a main window that adjusts its content as it's resized. Instead of using Windows Forms controls on a form, you�ll use WPF XAML controls.

Page 528:
In the header, change "Windows Store app" to "WPF application"

Page 532:
In the box that starts "Every program you've written...", change "Windows Store app" to "WPF application"

Page 680:
In the first line, change "In Chapter 14, we built" to "When you read through Chapter 14 in the book, you saw that we built"
And in the second paragraph of step 1, change "from the Windows Store app" to "from the Windows Store app we showed you in the book (you can download them from the book's website)"

Pages 726-727:
Fixed diagram of object model and first line of code to reflect WPF instead of Windows Store.

Page 750:
In the first line, change "Create a new Windows Store app" to "Create a new WPF application"

On page 820, don't we need to include the namespace Windows.UI.Core to use the KeyEventArgs class for our event handlers?

Note from the Author or Editor:
Yes, you do! Good catch.

On page 813, the Shot class has a private _direction field and a Direction property that you would assume serves to access the backing field, yet it has a standard get accessor that doesn't access the private field. The get accessor should either return _direction, or the private field should be gotten rid of and all occurrences replaced with the Direction property. The latter option is what is in the solution code.

On pages 790 and 791, a couple of notes (bottom of 790, "handwritten" on right side of 791) refer to the CreateFrameImages() method. I believe this is supposed to be referring to the StartAnimation() method.

Yield return example misses the last sport. Need to fix this line of code to change < to <= :

for (int i = 0; i <= maxEnumValue; i++) {

This:

int maxEnumValue = Enum.GetValues(typeof(Sport)).Length - 1;

Should be:

int maxEnumValue = Enum.GetValues(typeof(Sport)).Length;

because subtracting one from maxEnumValue prevents the loop from reaching the last item in the Sport enum (that last item is Fencing).

There are duplicate, nested checks for the value of the 'amount' parameter. As written, the line inside the 'if' statement that calls Console.WriteLine will never be reached.

The ReceiveCash() method should probably be:

public int ReceiveCash(int amount)
{
if (amount > 0)
{
Cash += amount;
return amount;
}
Console.WriteLine("{0} says: {1} is not an amount I'll take", Name, amount);
return 0;
}

This error is also in the second edition of the book.

These properties:

private Size _playAreaSize { get; set; }
private Size _hiveSize { get; set; }
private Size _flowerSize { get; set; }

Should be declared as fields. Unless a property contains code (i.e., it's not an automatic property), I don't think there's any reason to create a private property.

In this line:

double delta = 10 + Math.Max(1, Score * .5);

Math.Max() is superfluous because Score is an int that's initialized to zero and it's incremented by 1 each time the score is increased. Instead, you could just write:

double delta = 11 + (Score * .5); // parentheses are optional


Also in the NextHiveLocation() method, in this line:

_lastHiveLocation += delta * (_random.Next(2) == 0 ? 1 : -1);

The multiplication operation could be removed:

_lastHiveLocation += (_random.Next(2) == 0) ? delta : -delta;

The value of the _beeWidth field is assigned in the StartGame() method, but it's never used. It should be used, though, in the BeeLanded() method:

if ((beeLeft < _flowerLeft) || (beeLeft > _flowerLeft + _flowerWidth))

Should be:

if ((beeLeft + _beeWidth) < _flowerLeft || beeLeft > (_flowerLeft + _flowerWidth))

...because a bee will always be counted as missed if the bee's left edge is even one pixel less than the flower's left edge.

This:

int beeCount = _stars.Count;

Should be deleted because it's not used and, if it was, it should be:

int beeCount = _bees.Count;

This:

int beeCount = _random.Next(5, 10);

Should be:

int beeCount = _random.Next(5, 16);

Because the instructions on page 800 specify between 5 and 15 bees. In the Next() method, the first parameter is inclusive but the second parameter is exclusive, so to get 15 bees you have to pass in 16.


In that same method, this:

int s = _random.Next(50, 100);

Should be:

int s = _random.Next(40, 151);

Because the directions on page 800 specify a size between 40 and 150.


There's a similar error on page 803, in the CreateStars() method:

int starCount = _random.Next(5, 10);

Should be:

int starCount = _random.Next(5, 11);

Removed an unnecessary style from the <UserControl.Resources> section (<Style TargetType="TextBlock"> ... </Style>)

469 - in the left-hand annotation, the text "send the three weapon icons" is changed to "send the weapon and potion icons", and "player icons" is changed to "player icon"
476 - the fourth annotation is changed to: "The player?s constructor sets its HitPoints to 10 after the base constructor is called."
480 - missing semicolon in Weapon constructor (PickedUp = false;)
482 - the text "the potion?s Used() method" is changed to "the potion?s Used property"

In this project, it's not necessary for the RosterViewModel class to implement INotifyPropertyChanged. The app will not run any differently if you remove the OnPropertyChanged() method and remove the reference to that method in the TeamName setter.

Also, in the UpdateRosters() method it's not necessary to call Starters.Clear() or Bench.Clear().

Note from the Author or Editor:
You're absolutely right. I also added the following box to the bottom of the page:

In a typical MVVM app, only classes in the ViewModel implement INotifyPropertyChanged.
That's because the ViewModel contains the only objects that XAML controls are bound to. In this project, however, we didn't need to implement INotifyPropertyChanged because the bound properties are updated in the constructor. If you wanted to modify the project to let the Brian and Jimmy change their team names, you'd need to fire a PropertyChanged event in the TeamName set accessor.

The SettingsPane.GetForCurrentView().CommandsRequested event is being subscribed to in the constructor of MainPage. This results in a duplicate "About" command being added to the Settings pane every time the app returns from another page.

I'm not sure of the best way to fix this, but in this case you could add a line of code at the beginning of the CommandsRequested event handler which checks to see if at least one command has already been added to the settings pane:

void MainPage_CommandsRequested(SettingsPane sender,
SettingsPaneCommandsRequestedEventArgs args)
{
if (args.Request.ApplicationCommands.Count > 0) return;
....
]

Note from the Author or Editor:
Nice catch! I decided to use a static field because it's easier for the reader to understand. I also added an annotation telling the reader to try removing the line that sets the field to true, so they can see the multiple commands added to the Settings charm.

static bool aboutCommandAdded = false;
public MainPage() {
this.InitializeComponent();
if (!aboutCommandAdded) {
SettingsPane.GetForCurrentView().CommandsRequested += MainPage_CommandsRequested;
aboutCommandAdded = true;
}
}

In ComicQueryManage.cs, this line:

CurrentQueryResults.Clear();

Should be removed from these methods:

- LinqMakesQueriesEasy (page 662)
- ExpensiveComics (page 662)
- LinqIsVersatile1 (page 669)
- LinqIsVersatile2 (page 669)

Calling CurrentQueryResults.Clear() is redundant because a new instance of CurrentQueryResults is being created in the class's constructor.

It might be better to add a note that explains what the Clear() method does and why it's not necessary in this case.

Note from the Author or Editor:
Agreed. I made the change, and added a box that helps explain what's going on:

The CurrentQueryResults property is used to display the query results with data binding. It doesn?t need to be cleared because a new page object is created each time page navigation occurs, and it has its own new instance of ComicQueryManager, with a newly created empty collection.

The third RowDefinition should be deleted because no controls are added to it.