cs11dotnet7/docs/errata/errata.md

Errata (22 items)

If you find any mistakes, then please raise an issue in this repository or email me at markjprice (at) gmail.com.

Microsoft has changed their domain for documentation from https://docs.microsoft.com to https://learn.microsoft.com with an automatic redirect so all links in my books that use the docs domain should still work.

• Page 4, 8 - Pros and cons of the .NET Interactive Notebooks extension, Downloading and installing Visual Studio Code
• Page 11 - Understanding the journey to one .NET and Understanding .NET support
• Page 37 - Getting definitions of types and their members
• Page 83 - Formatting using numbered positional arguments
• Page 83 - Formatting using interpolated strings
• Page 85 - Getting text input from the user
• Page 86 - Getting text input from the user
• Page 114 - Simplifying switch statements with switch expressions
• Page 185 - Creating a class library that needs testing
• Page 188 - Running unit tests using Visual Studio Code
• Page 244 - Init-only properties
• Page 272 - Defining struct types
• Page 275 - Releasing unmanaged resources
• Page 322 - Revealing the location of a type
• Page 330 - Publishing a self-contained app, Page 354 - Exercise 7.3 – Explore PowerShell
• Page 412 - Compressing streams
• Page 477 - Inserting entities
• Page 627 - Defining a typed view
• Page 631 - Passing parameters using a route value
• Page 641 - Enabling role management and creating a role programmatically
• Page 649 - Varying cached data by query string
• Page 707 - Reviewing the Blazor Server project template
• Page 733 - Building customer create, edit, and delete components

Page 4, 8 - Pros and cons of the .NET Interactive Notebooks extension, Downloading and installing Visual Studio Code

The .NET Interactive Notebooks extension has been renamed to Polyglot Notebooks. It still retains its original identifier ms-dotnettools.dotnet-interactive-vscode. The engine is still named .NET Interactive.

Read more here: https://devblogs.microsoft.com/dotnet/dotnet-interactive-notebooks-is-now-polyglot-notebooks/#why-the-name-change

I wrote that "They cannot read input from the user, for example, you cannot use ReadLine or ReadKey." Although you cannot use the Console class methods, you can use the Microsoft.DotNet.Interactive.Kernel class and its GetInputAsync method. This uses the Visual Studio Code user interface to prompt the user for input.

Page 11 - Understanding the journey to one .NET and Understanding .NET support

Even-numbered .NET releases like .NET 6 and .NET 8 have a support level named Long Term Support (LTS) with a duration of 3 years. Odd-numbered .NET releases like .NET 5 and .NET 7 had a support level named Current with a duration of 18 months.

On June 6, 2022, the .NET team proposed to change the support level name from Current to Short Term Support (STS) to complement the existing Long Term Support (LTS). I updated the drafts of my book to reflect that change.

On October 11, 2022, the .NET team changed the name again, to Standard Support, probably because Microsoft Marketing decided that "short term" sounded too negative. My editors and I scrambled to update the final drafts of my book to reflect that change.

On October 28, 2022, the .NET team changed the name again, to Standard Term Support (STS), probably because an initialism of SS is problematic and internal code and configuration was already using sts. Sadly, it was too late to update the PDFs that are sent to print.

Sigh. Such are the perils of trying to be up-to-date on release day.

Page 37 - Getting definitions of types and their members

In Step 3, I wrote, "Click inside int and then right-click and choose Go To Definition."

Visual Studio 2022 used to show code reverse-engineered from metadata for the selected type like int (see Figure 1.1), including the comments that I talk about in the book, but it now shows Source Link code (see Figure 1.2) which does not have comments.

Figure 1.1: Go To Definition file tab generated from metadata

Figure 1.2: Go To Definition file tab retrieved from embedded Source Link code

To change back to the original Visual Studio 2022 behavior that is described in the book, please follow these steps:

1. In Visual Studio 2022, navigate to Tools | Options.
2. In the Options dialog, navigate to Text Editor | C# | Advanced.
3. In the Go To Definition section, clear the check box named Enable navigation to Source Link and Embedded sources, as shown in Figure 1.3.
4. Click OK.

Figure 1.3: Disabling Source Link for the Go To Definition feature

Page 83 - Formatting using numbered positional arguments

At the end of the section, I say, "The Write, WriteLine, and Format methods can have up to four numbered arguments, named arg0, arg1, arg2, and arg3."

But the methods can only have up to three named arguments. I should have said, "The Write, WriteLine, and Format methods can have up to three numbered arguments, named arg0, arg1, and arg2. If you need to pass more than three values, then you cannot name the arguments using arg0 and so on, as shown in the following code:"

// Passing three values can use named arguments.
Console.WriteLine(
 format: "{0} {1} lived in {2}.", 
 arg0: "Roger", arg1: "Cevung", arg2: "Stockholm");

// Passing four or more values cannot use named arguments.
Console.WriteLine(
 "{0} {1} lived in {2} and worked in the {3} team at {4}.", 
 "Roger", "Cevung", "Stockholm", "Education", "Optimizely");

Page 83 - Formatting using interpolated strings

In Step 1, you enter some statements to output some variables using an interpolated string, as shown in the following code:

// The following statement must be all on one line.
Console.WriteLine($"{numberOfApples} apples cost {pricePerApple * numberOfApples:C}");

The comment says that it "must be all on one line". This is true for C# 10 and earlier (which is the default compiler if you target .NET 6), but if you use C# 11 then an expression inside an interpolation hole like {pricePerApple * numberOfApples:C} can now include line breaks. So we can, for example, enter the statement like this:

// The following statement must be all on one line when using C# 10 or earlier.
// If using C# 11, we can include a line break, as shown here:
Console.WriteLine($"{numberOfApples} apples cost {pricePerApple 
  * numberOfApples:C}");

Page 85 - Getting text input from the user

I wrote that a notebook "does not support reading input from the console using Console.ReadLine()." Although this is true, you can use the Microsoft.DotNet.Interactive.Kernel class and its GetInputAsync method instead. This uses the .NET Interactive integration with the Visual Studio Code user interface to prompt the user for input.

using Microsoft.DotNet.Interactive; // to use the Kernel class

string firstName = await Kernel.GetInputAsync("Type your first name: ");

string age = await Kernel.GetInputAsync("Type your age: ");

Console.WriteLine($"Hello {firstName}, you look good for {age}.");

Page 86 - Getting text input from the user

In Step 3, I wrote, "For the firstName variable" when I should have written, "For the age variable".

Page 114 - Simplifying switch statements with switch expressions

Thanks to Ricky for raising this issue on 25 January 2023.

In Step 1, the code statement that outputs the four-legged cat information is missing the word "named", as shown in the following code:

Cat fourLeggedCat when fourLeggedCat.Legs == 4
  => $"The cat {fourLeggedCat.Name} has four legs.",

It should be:

Cat fourLeggedCat when fourLeggedCat.Legs == 4
  => $"The cat named {fourLeggedCat.Name} has four legs.",

Page 185 - Creating a class library that needs testing

In the "If you are using Visual Studio Code" section, in Step 5, the command in the book is dotnet new console but it should have been dotnet new classlib.

Page 188 - Running unit tests using Visual Studio Code

Thanks to kwatsonkairosmgt for raising this issue on 27 October 2022.

In Step 1, the project name CalculatorLibUnitTest should be CalculatorLibUnitTests.

Page 244 - Init-only properties

Thanks to Bob Molloy for raising this issue via email.

In Step 1, I say to add a new file named Records.cs to the PacktLibraryNetStandard2 project/folder. I should have said to the PacktLibraryModern project/folder.

Page 272 - Defining struct types

Thanks to Ali Koleiny Zadeh for raising this issue on 15 January 2023.

In Step 4, the output should be formatted using the "command line" style like in Step 6 instead of the "code" style so that it has the black background.

Page 275 - Releasing unmanaged resources

Thanks to Wuu#0348 on the Packt Discord channels for raising this issue.

In the second bullet point after the large code block, I wrote, "It needs to check the disposing parameter and disposed field because if the finalizer thread has already run and it called the ~ObjectWithUnmanagedResources method, then only unmanaged resources need to be deallocated." I should have written managed not unmanaged.

It might be clearer if I wrote, "It needs to check the disposing parameter and disposed field because if the finalizer thread has already run and it called the ~ObjectWithUnmanagedResources method, then unmanaged resources will already have been deallocated and only managed resources remain to be deallocated by the garbage collector." I will do this in the next edition.

Page 322 - Revealing the location of a type

Thanks to Bob Molloy for raising this issue via email.

In Steps 2 and 5, I say to "Navigate to the top of the code file and note the assembly filename..."

If you have Source Link enabled, then you will not see the filename. I recommend that you disable Source Link.

If you have Source Link disabled, then to see the filename you must expand the collapsed region. You will then find the assembly filename within the region, as shown in the following code:

#region Assembly System.Runtime, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
// C:\Program Files\dotnet\packs\Microsoft.NETCore.App.Ref\7.0.0\ref\net7.0\System.Runtime.dll
#endregion

Page 330 - Publishing a self-contained app, Page 354 - Exercise 7.3 – Explore PowerShell

In the Good Practice box on page 330, I wrote about how you can automate commands using scripts written in the PowerShell language. My original plan was to write content about PowerShell in the GitHub repository. But PowerShell is a massive topic and there will always be higher priority content to create that is specifically about C# and .NET. In the next edition I will just reference the official PowerShell documentation: https://learn.microsoft.com/en-us/powershell/ And I will remove Exercise 7.3 that suggests exploring PowerShell.

Page 412 - Compressing streams

Thanks to Bob Molloy for raising this issue via email.

In Step 2, the following statement enables interpolated strings unnecessarily:

WriteLine($"The compressed contents:");

It should be:

WriteLine("The compressed contents:");

Page 477 - Inserting entities

Thanks to Chadwick Geyser for raising this issue on 29 November 2022.

In Step 4, the code statement to list the products uses an older version of the method signature that I removed before publishing that only allows a single productId to be highlighted, as shown in the following code:

ListProducts(productIdToHighlight: resultAdd.productId);

It should use the method signature that allows multiple productIds to be highlighted, as shown in the following code:

ListProducts(productIdsToHighlight: new[] { resultAdd.productId });

Page 627 - Defining a typed view

Thanks to Chadwick Geyser for raising this issue on 4 December 2022.

In Step 3, the code in the book to render the carousel indicators has an incorrect attribute named data-slide-to, as shown in the following markup:

<li data-bs-target="#categories" data-slide-to="@c" 
    class="@currentItem"></li>

Should be data-bs-slide-to, as shown in the following markup:

<li data-bs-target="#categories" data-bs-slide-to="@c" 
    class="@currentItem"></li>

It was already correct in the GitHub copy of the code.

Page 631 - Passing parameters using a route value

Thanks to Bob Molloy for raising this issue via email.

In Step 3, the statements attempt to output the values of the category name and unit price for the product, as shown in the following markup:

<dt>Category</dt>
<dd>@Model.CategoryId - @Model.Category.CategoryName</dd>
<dt>Unit Price</dt>
<dd>@Model.UnitPrice.Value.ToString("C")</dd>

But since the Category and UnitPrice properties could be null, we should use a null checks, as shown in the following markup:

<dt>Category</dt>
<dd>@Model.CategoryId - @Model.Category?.CategoryName</dd>
<dt>Unit Price</dt>
<dd>@(Model.UnitPrice is null ? "zero" : Model.UnitPrice.Value.ToString("C"))</dd>

Page 641 - Enabling role management and creating a role programmatically

Thanks to Bob Molloy for raising this issue via email.

In Step 2, in the Index action method, the variable declaration for finding the email of the user is not nullable, as shown in the following code:

IdentityUser user = await userManager.FindByEmailAsync(UserEmail);

It should be nullable, as shown in the following code:

IdentityUser? user = await userManager.FindByEmailAsync(UserEmail);

It was already correct in the GitHub copy of the code.

Page 649 - Varying cached data by query string

Thanks to Chadwick Geyser for raising this issue on 5 December 2022.

In Step 1, when defining a policy for output caching, the statement uses the method VaryByQuery, as shown in the following code:

options.AddPolicy("views", p => p.VaryByQuery(""));

The method name changed in Release Candidate 2, as described here, so statement should be changed to use the new method SetVaryByQuery, as shown in the following code:

options.AddPolicy("views", p => p.SetVaryByQuery(""));

Page 707 - Reviewing the Blazor Server project template

Thanks to Bob Molloy for raising this issue on 19 December 2022.

In Steps 6 and 7, I wrote that there are two files that combine to product the home page for a Blazor Server project, named _Host.cshtml and _Layout.cshtml.

Microsoft changed this project template to merge them together so there is no shared layout file named _Layout.cshtml. The markup is now all in the _Host.cshtml file, as shown in the following markup:

@page "/"
@using Microsoft.AspNetCore.Components.Web
@namespace Northwind.BlazorServer.Pages
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <base href="~/" />
    <link rel="stylesheet" href="css/bootstrap/bootstrap.min.css" />
    <link href="css/site.css" rel="stylesheet" />
    <link href="Northwind.BlazorServer.styles.css" rel="stylesheet" />
    <link rel="icon" type="image/png" href="favicon.png"/>
    <component type="typeof(HeadOutlet)" render-mode="ServerPrerendered" />
</head>
<body>
    <component type="typeof(App)" render-mode="ServerPrerendered" />

    <div id="blazor-error-ui">
        <environment include="Staging,Production">
            An error has occurred. This application may no longer respond until reloaded.
        </environment>
        <environment include="Development">
            An unhandled exception has occurred. See browser dev tools for details.
        </environment>
        <a href="" class="reload">Reload</a>
        <a class="dismiss">🗙</a>
    </div>

    <script src="_framework/blazor.server.js"></script>
</body>
</html>

Page 733 - Building customer create, edit, and delete components

Thanks to Bob Molloy for raising this issue on 27 December 2022.

In Step 4, in the file named EditCustomer.razor, the code for the Update method is missing the last statement to navigate to the customers page component after updating the customer in the database, as shown in the following code:

private async Task Update()
{
  if (customer is not null)
  {
    await service.UpdateCustomerAsync(customer);
  }

  navigation.NavigateTo("customers");
}