If you find any mistakes, then please [raise an issue in this repository](https://github.com/markjprice/cs11dotnet7/issues) 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-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-11---understanding-the-journey-to-one-net-and-understanding-net-support)
- [Page 166 - Setting a breakpoint and starting debugging - Using Visual Studio 2022](#page-166---setting-a-breakpoint-and-starting-debugging---using-visual-studio-2022)
- [Page 641 - Enabling role management and creating a role programmatically](#page-641---enabling-role-management-and-creating-a-role-programmatically)
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*.
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.
In the table, the **C# for Visual Studio Code** extension says it is "powered by OmniSharp". This is true up to the most recent release version `1.25.9`. But if you install the pre-release version `2.0.x` then it does not include OmniSharp any more.
To follow the instructions in the book, if you have installed the pre-release version `2.0.x` then on the **C#** extension page, I recommend that you click the button **Switch to Release Version** to revert back to the current release version `1.25.9`.
If you have installed the **C# Dev Kit** then it will install the pre-release version of the **C#** extension. If you want to use them, then I have written [instructions in the improvements page](https://github.com/markjprice/cs11dotnet7/blob/main/docs/errata/improvements.md#page-31---adding-a-second-project-using-visual-studio-code) and I will use these in the next edition.
> **More Information**: You can read the announcement about **C# Dev Kit** at the following link: https://devblogs.microsoft.com/visualstudio/announcing-csharp-dev-kit-for-visual-studio-code/
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)**](https://github.com/dotnet/announcements/issues/223) 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**](https://devblogs.microsoft.com/dotnet/announcing-dotnet-7-rc-2/#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)**](https://twitter.com/mairacw/status/1585789100879069185), 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.
In Step 18, I wrote, "Visual Studio Code may have to download and install C# dependencies like OmniSharp, .NET Core Debugger, and Razor Language Server". This is true up to the most recent release version `1.25.9`. But if you install the pre-release version `2.0.x` then it does not include OmniSharp any more.
To follow the instructions in the book, if you have installed the pre-release version `2.0.x` then on the **C#** extension page, I recommend that you click the button **Switch to Release Version** to revert back to the current release version `1.25.9`.
# Page 31 - Adding a second project using Visual Studio Code
In Step 7, I wrote, "Enter `omni`, and then, in the drop-down list that appears, select **OmniSharp: Select Project**."
This works if you installed the most recent release version `1.25.9`. But if you installed the pre-release version `2.0.x` then it does not include OmniSharp any more.
To follow the instructions in the book, if you have installed the pre-release version `2.0.x` then on the **C#** extension page, I recommend that you click the button **Switch to Release Version** to revert back to the current release version `1.25.9`.
Interestingly, `dotnet help help` opens a web browser for the `help` command, and `dotnet help -h` outputs documentation for the `help` command at the command-line!
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.
> Thanks to [Papa Smurf](https://github.com/GoPapaSmurf) for raising this [issue on 31 March 2023](https://github.com/markjprice/cs11dotnet7/issues/53).
At the end of the last paragraph, I mention a method that can determine if a number value is *not-a-number*. The method name was written in the book as `IsNan`. It should be `IsNaN`.
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:"
In Step 1, you enter some statements to output some variables using an interpolated string, as shown in the following code:
```cs
// The following statement must be all on one line.
Console.WriteLine($"{numberOfApples} apples cost {pricePerApple * numberOfApples:C}");
```
The comment says that it "must be all on one line". This is true for C# 10 and earlier (which is the default compiler if you target .NET 6), but if you use C# 11 then an expression inside an interpolation hole like `{pricePerApple * numberOfApples:C}` can now include line breaks. So we can, for example, enter the statement like this:
```cs
// The following statement must be all on one line when using C# 10 or earlier.
// If using C# 11, we can include a line break, as shown here:
Console.WriteLine($"{numberOfApples} apples cost {pricePerApple
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.
```cs
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}.");
```
> Thanks to Norbert Duenki who raised this issue by email on 4 April 2023.
In Step 3, I wrote, "As an optional challenge, add statements so that the user can only make ten attempts before
an error message is displayed."
In my code solution in GitHub, I made a mistake in my logic so that if the user entered the correct password on their tenth attempt, it output the error message.
I have updated the logic to fix this issue, as well as to use variables to store the actual password and the maximum number of attempts, as shown in the following code:
```cs
// Looping with the do statement
string? actualPassword = "Pa$$w0rd";
string? password;
int maximumAttempts = 10;
int attempts = 0;
do
{
attempts++;
Write("Enter your password: ");
password = ReadLine();
}
while ((password != actualPassword) & (attempts <maximumAttempts));
if (password == actualPassword)
{
WriteLine("Correct!");
}
else
{
WriteLine("You have used {0} attempts! The password was {1}.",
# Page 156 - Calculating factorials with recursion
> Thanks to [Ricky](https://github.com/r1c5) for raising this [issue on 29 January 2023](https://github.com/markjprice/cs11dotnet7/issues/21).
In Step 1, in the third bullet that explains the code, I wrote, "If the input parameter number is more than 1, which it will be in all other cases..." I should have written, "If the input parameter number is more than 0, which it will be in all other cases..."
# Page 166 - Setting a breakpoint and starting debugging - Using Visual Studio 2022
> Thanks to [Masoud Nazari](https://github.com/MAS-OUD) for raising this [issue on 12 February 2023](https://github.com/markjprice/cs11dotnet7/issues/28).
At the end of this section I wrote, "If you do not want to see how to use Visual Studio Code to start debugging, then you can skip the next section and continue to the section titled *Navigating with the debugging toolbar*."
But the immediately following section is *Navigating with the debugging toolbar*. The paragraph should move to after this section and before the section titled *Using Visual Studio Code*, and it should say, "If you do not want to see how to use Visual Studio Code to start debugging, then you can skip the next section and continue to the section titled *Debugging windows*."
> Thanks to [Nick Bettes](https://github.com/bettesn) and [Zhang Cheng](https://github.com/Matrix-Zhang) for raising this issue on [16 February 2023](https://github.com/markjprice/cs11dotnet7/issues/29), a special thanks to [Huynh Loc Le](https://github.com/huynhloc-1110), who identified that the issue was caused by a Microsoft fix to one of their bugs, and finally thanks to [richshi](https://github.com/richshi) who raised this issue again on [28 June 2023](https://github.com/markjprice/cs11dotnet7/issues/76) and consequently made me dig deeper to find a more complete explanation and solution.
In Step 1, you add package references to enable an `appsettings.json` file to configure a trace switch. If you reference `Microsoft.Extensions.Configuration.Binder` package versions `7.0.3` or later, then they have fixed a bug, but the fix causes a regression in expected behavior which means that unless we change how we set the trace switch level an exception will be thrown, as shown in the following output:
Originally, it seemed the best solution was to avoid the later versions that cause the changed behavior, so I advised to use 7.0.2 or earlier. But the change in 7.0.3 was to fix a bug, so we really need a solution that will allow us to use the latest package version and also works for older versions too.
See also this common mistake item: https://github.com/markjprice/cs11dotnet7/blob/main/docs/errata/common-errors.md#microsoft-introduces-a-bug-in-a-later-version
> Thanks to [TheKuroEver](https://github.com/TheKuroEver) for raising this [issue on 7 March 2023](https://github.com/markjprice/cs11dotnet7/issues/37).
In Step 6, I tell you to write a statement to add the `appsettings.json` file to the configuration builder so that it can be used to set the trace switch level. But in the print book, it sets the `optional` parameter to `true` when it should be `false`.
Fix the issue by setting the `optional` parameter to `false`, as shown in the following code:
```cs
builder.AddJsonFile("appsettings.json",
optional: false, reloadOnChange: true);
```
> The statement was already correct in GitHub: https://github.com/markjprice/cs11dotnet7/blob/main/vs4win/Chapter04/Instrumenting/Program.cs#L28
The `optional` parameter controls if the statement throws an exception at runtime if the file is missing. We want to ensure that we are notified with an exception if the file is missing, for example, as shown in the following output:
```
Reading from appsettings.json in C:\cs11dotnet7\Chapter04\Instrumenting\bin\Debug\net7.0
Unhandled exception. System.IO.FileNotFoundException: The configuration file 'appsettings.json' was not found and is not optional. The expected physical path was 'C:\cs11dotnet7\Chapter04\Instrumenting\bin\Debug\net7.0\appsettings.json'.
at Microsoft.Extensions.Configuration.FileConfigurationProvider.HandleException(ExceptionDispatchInfo info)
at Microsoft.Extensions.Configuration.FileConfigurationProvider.Load(Boolean reload)
at Microsoft.Extensions.Configuration.FileConfigurationProvider.Load()
at Microsoft.Extensions.Configuration.ConfigurationRoot..ctor(IList`1 providers)
at Microsoft.Extensions.Configuration.ConfigurationBuilder.Build()
at Program.<Main>$(String[] args) in C:\cs11dotnet7\Chapter04\Instrumenting\Program.cs:line 30
```
If we set the `optional` parameter to `true` and the `appsettings.json` file is missing then this exception will not be thrown BUT the trace switch will not be set by the file and therefore defaults to `Off`. Therefore no output is written to the `log.txt` file on the desktop for the trace switch.
In the next edition, I will add a statement after binding to the packt switch configuration that outputs the trace switch level to the `Console` to make it clearer when there might be a problem because either the trace switch is set to `Off` or the `appsettings.json` file is missing and it has been made optional, as shown in the following code:
# 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`.
> Thanks to [kwatsonkairosmgt](https://github.com/kwatsonkairosmgt) for raising this [issue on 27 October 2022](https://github.com/markjprice/cs10dotnet6/issues/106).
In Step 1, the project name `CalculatorLibUnitTest` should be `CalculatorLibUnitTests`.
# Page 231 - Requiring properties to be set during instantiation
> Thanks to [Masoud Nazari](https://github.com/MAS-OUD) for raising this [issue on 1 March 2023](https://github.com/markjprice/cs11dotnet7/issues/33).
In Step 1, you are told to add a new class library project named `PacktLibraryModern`.
In Step 4, in the `PeopleApp` console app project, you are told to create an instance of the `Book` class that is defined in the class library. To do so, you must have added a reference to the `PacktLibraryModern` project.
In the next edition, I will add steps before Step 4 to remind readers how to do this, as shown below:
*If you are using Visual Studio 2022:*
- In **Solution Explorer**, select the `PeopleApp` project, navigate to **Project** | **Add Project Reference…**, check the box to select the **PacktLibraryModern** project, and then click **OK**.
*If you are using Visual Studio Code:*
- Edit `PeopleApp.csproj` to add a project reference to `PacktLibraryModern`, as shown in
> Thanks to [cgwid](https://github.com/cgwid) for raising this [issue on 12 April 2023](https://github.com/markjprice/cs11dotnet7/issues/59).
In this section, we define some methods and operators so that two `Person` objects can get married and have babies. The example we model comes from the Bible story of Lamech and his two wives and their children. But the code I tell you to write does not allow Lamech to marry two women so later an exception is thrown when Lamech and his second wife try to make a baby.
cgwid suggested a solution in [the issue they raised](https://github.com/markjprice/cs11dotnet7/issues/59). I want to rethink this code example for the next edition to avoid it becoming overly complex so I will leave it to the reader to decide how they might want to solve it. Meanwhile, I have added an improvement with suggested alternative code here: https://github.com/markjprice/cs11dotnet7/blob/main/docs/errata/improvements.md#page-235---more-about-methods
# Page 244 - Enhancements to pattern matching in C# 9 or later
> Thanks to [Noel Arzola Jr](https://github.com/NoelArzola) for raising this [issue on 22 October 2023](https://github.com/markjprice/cs11dotnet7/issues/87).
At the end of this section, I wrote, "You could also use the relational pattern in combination with the property pattern to avoid the nested
switch expression, as shown in the following code:"
> 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.
In Step 2, if you use Visual Studio 2022 to create the class file then it will have multiple statements of existing code. These statements should be deletd and replaced with the code as shown in Step 3. If you just add new statements inside those created by Visual Studio 2022 then it won't work because the `partial Program` class needs to be in the default empty namespace just like the auto-generated `Program` class is.
A similar issue is covered by these improvement items:
> Thanks to [Ricky](https://github.com/r1c5) for raising this [issue on 2 February 2023](https://github.com/markjprice/cs11dotnet7/issues/23).
In Step 5, the statement that outputs the "Stop it!" message uses the `$` string interpolation prefix character unnecessarily, as shown in the following code:
```cs
WriteLine($"Stop it!");
```
The `$` can be removed, as shown in the following code:
# Page 263 - Comparing objects using a separate class
> Thanks to [Masoud Nazari](https://github.com/MAS-OUD) for raising this [issue on 15 March 2023](https://github.com/markjprice/cs11dotnet7/issues/43).
In Step 1, the following comment has an extra slash:
> Thanks to [Ali Koleiny Zadeh](https://github.com/alikzalikz) for raising this [issue on 15 January 2023](https://github.com/markjprice/cs11dotnet7/issues/18).
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.
> 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.
> Thanks to [Ricky](https://github.com/r1c5) for raising this [issue on 2 February 2023](https://github.com/markjprice/cs11dotnet7/issues/24).
In Step 6, the output should be formatted with a black background like other command-line blocks, and the output is missing the writing of the variable named `thisCannotBeNull`. The output should be:
```
4
0
7
7
```
Step 7 should therefore say, "The **second** line is blank because it is outputting the null value!", and it should not be formatted as a numbered step because it is a not an instruction to the reader, it is a note.
# Page 279 - Declaring non-nullable variables and parameters
> Thanks to [Ricky](https://github.com/r1c5) for raising this [issue on 19 February 2023](https://github.com/markjprice/cs11dotnet7/issues/30).
In Step 1, I wrote, "In `NullHandling.csproj`," which could be confusing because you do not need to modify that file. I should have written, "In the `NullHandling` project," because you need to add a new file to the project.
> 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](#page-37---getting-definitions-of-types-and-their-members).
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:
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.
> Thanks to [Masoud Nazari](https://github.com/MAS-OUD) for raising this [issue on 25 March 2023](https://github.com/markjprice/cs11dotnet7/issues/50).
In Step 2, I show the default formatting for complex numbers i.e. using round brackets and commas, as well as a custom format, as shown in the following output:
```
(4, 2) added to (3, 7) is (7, 9)
4 + 2i added to 3 + 7i is 7 + 9i
```
> See the official documentation for the `Complex.ToString` method here: https://learn.microsoft.com/en-us/dotnet/api/system.numerics.complex.tostring
Although this is the behavior in .NET 6, in .NET 7 (and .NET 8 previews), the formatting of complex numbers uses angle brackets and semi-colons, as shown in the following output:
```
<4;2> added to <3;7> is <7;9>
4 + 2i added to 3 + 7i is 7 + 9i
```
In the next edition, I will add a note about this. Since the official documentation still shows the behavior of .NET 6, this seems odd. My guess is that they decided to change to angle brackets and semi-colons because some cultures use round brackets to indicate negative numbers and use commas for decimal numbers. Therefore it would be confusing to have a mix of round brackets and commas meaning different things. Its a shame the documentation does not explain this and show the .NET 7 and later new default formats.
> Thanks to [Dario Bosco](https://github.com/DarioBosco) for raising this [issue on 6 February 2023](https://github.com/markjprice/cs11dotnet7/issues/26).
In Step 1, in the second bullet, I wrote, "Check for the existence of the custom directory path using the `Exists` method of the
`Directory` class." But in the code I used the `Exists` method of the `Path` class. We have statically imported both the `Path` and the `Directory` classes and they both have an `Exists` method in .NET 7. If we try to call an `Exists` method without a classname prefix we get a compile error due to ambiguity of which one to call. After writing the second bullet text, I changed the code from using `Directory` to using `Path` simply because it is shorter. In the 8th edition, I will add a note about this since it is useful for the reader to understand my choice and how the reader could have done it differently.
> Note: the `Path.Exists` method was added in .NET 7. It is not available in earlier versions of .NET.
# Page 454 - Scaffolding models using an existing database
> Thanks to [Masoud](https://github.com/MAS-OUD) for raising this [issue on 6 April 2023](https://github.com/markjprice/cs11dotnet7/issues/54).
## Category class changes
In Step 5, I show the class that represents a `Category` in the Northwind database that is generated by the `dotnet-ef`, as shown in the following code:
```cs
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using Microsoft.EntityFrameworkCore;
namespace WorkingWithEFCore.AutoGen
{
[Index("CategoryName", Name = "CategoryName")]
public partial class Category
{
public Category()
{
Products = new HashSet<Product>();
}
[Key]
public int CategoryId { get; set; }
[StringLength(15)]
public string CategoryName { get; set; }
[Column(TypeName = "ntext")]
public string? Description { get; set; }
[Column(TypeName = "image")]
public byte[]? Picture { get; set; }
[InverseProperty("Category")]
public virtual ICollection<Product> Products { get; set; }
}
}
```
The current `dotnet-ef` tool generates slightly different output, for example, it uses a file-scoped namespace declaration to avoid indenting and it initializes the `Products` property to a `List<T>` instead of a `HashSet<T>`, as shown in the following code:
```cs
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using Microsoft.EntityFrameworkCore;
namespace WorkingWithEFCore.AutoGen;
[Index("CategoryName", Name = "CategoryName")]
public partial class Category
{
[Key]
public int CategoryId { get; set; }
[StringLength(15)]
public string CategoryName { get; set; } = null!;
[Column(TypeName = "ntext")]
public string? Description { get; set; }
[Column(TypeName = "image")]
public byte[]? Picture { get; set; }
[InverseProperty("Category")]
public virtual ICollection<Product> Products { get; } = new List<Product>();
}
```
## NorthwindDb class changes
In Step 7, I show the class that represents the Northwind database that was generated by the `dotnet-ef` tool. The current `dotnet-ef` tool generates slightly different output, for example, it uses a file-scoped namespace declaration to avoid indenting and it does not set each `DbSet<T>` property to the null-forgiving operator, as shown in the following code:
```cs
// older version of dotnet-ef did this:
public virtual DbSet<Category> Categories { get; set; } = null!;
// current version of dotnet-ef does this:
public virtual DbSet<Category> Categories { get; set; }
> Thanks to [Chadwick Geyser](https://github.com/chadgdotme) for raising this [issue on 29 November 2022](https://github.com/markjprice/cs11dotnet7/issues/5).
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:
> Thanks to [Masoud](https://github.com/MAS-OUD) for raising this [issue on 20 April 2023](https://github.com/markjprice/cs11dotnet7/issues/62).
In Steps 3 and 5, the screenshots in *Figure 11.1* and *Figure 11.2* show a solution name of **Chapter12** when it should be **Chapter11**. In the next edition, I will retake the screenshots.
# Page 548 - Creating a class library for a Northwind database context
In Step 11, you write an extension method that registers the `NorthwindContext` class for use as a dependency service. In later chapters, this will be used in ASP.NET Core and Blazor projects. By default, a `DbContext` class is registered using `Scope` lifetime, meaning that multiple threads can share the same instance. If more than one thread attempts to use the same `NorthwindContext` class instance at the same time then you will see the following runtime exception thrown:
> "A second operation started on this context before a previous operation completed. This is usually caused by different threads using the same instance of a DbContext, however instance members are not guaranteed to be thread safe."
To avoid this, we should register the `NorthwindContext` class with a `Transient` lifetime, as shown in the following code:
```cs
using Microsoft.EntityFrameworkCore; // UseSqlite
using Microsoft.Extensions.DependencyInjection; // IServiceCollection
namespace Packt.Shared;
public static class NorthwindContextExtensions {
/// <summary>
/// Adds NorthwindContext to the specified IServiceCollection. Uses the Sqlite database provider.
/// </summary>
/// <paramname="services"></param>
/// <paramname="relativePath">Set to override the default of ".."</param>
/// <paramname="databaseFilename">Set to override the default of "Northwind.db"</param>
/// <returns>An IServiceCollection that can be used to add more services.</returns>
public static IServiceCollection AddNorthwindContext(
If you get the error, "The certificate chain was issued by an authority that is not trusted.", then it is because the connection to the SQL Server database will be encrypted by default but the OS and therefore the app does not (yet) trust the local development server certificate.
You have three choices to fix this issue:
1. Add the following to the database connection string to make the certicate trusted for this connection:
```
TrustServerCertificate=true;
```
2. Add the following to the database connection string to disable encryption so it does not need to trust the certificate for this connection:
```
Encrypt=false;
```
3. Run the following at the command-line to trust the certificate for all .NET apps in future:
# Page 551 - Creating a class library for entity models using SQL Server
In Step 15, you write an extension method that registers the `NorthwindContext` class for use as a dependency service. In later chapters, this will be used in ASP.NET Core and Blazor projects. By default, a `DbContext` class is registered using `Scope` lifetime, meaning that multiple threads can share the same instance. If more than one thread attempts to use the same `NorthwindContext` class instance at the same time then you will see the following runtime exception thrown:
> "A second operation started on this context before a previous operation completed. This is usually caused by different threads using the same instance of a DbContext, however instance members are not guaranteed to be thread safe."
To avoid this, we should register the `NorthwindContext` class with a `Transient` lifetime, as shown in the following code:
```cs
using Microsoft.EntityFrameworkCore; // UseSqlServer
using Microsoft.Extensions.DependencyInjection; // IServiceCollection
namespace Packt.Shared;
public static class NorthwindContextExtensions {
/// <summary>
/// Adds NorthwindContext to the specified IServiceCollection. Uses the SqlServer database provider.
/// </summary>
/// <paramname="services"></param>
/// <paramname="connectionString">Set to override the default.</param>
/// <returns>An IServiceCollection that can be used to add more services.</returns>
public static IServiceCollection AddNorthwindContext(
> Note that I have also written a related improvement here: https://github.com/markjprice/cs11dotnet7/blob/main/docs/errata/improvements.md#page-551---creating-a-class-library-for-entity-models-using-sql-server
> Thanks to Peter Haugstad for sending this issue via email on December 5, 2023.
At the bottom of page 623, I wrote, "The `<a>` elements use Tag Helper attributes named `asp-controller` and `asp-action` to specify the controller name and action name that will execute when the link is clicked on. If you want to navigate to a feature in a Razor Class Library, like the employees component that you created in the previous chapter, then you use `asp-area` to specify the feature name."
I mixed up incompatible technologies. The `<a>` Tag Helper only works with MVC, not Razor Pages. My example of the employees component was therefore wrong because it is a Razor Page component, not an MVC component. You cannot set the `asp-controller` and `asp-action` attributes to navigate to the employees component.
If you want to navigate to the employees component from an MVC view, then you must use similar syntax to what we used in *Chapter 13*, as shown in the following markup without Tag Helpers:
In the next edition, I will delete the following sentence, "If you want to navigate to a feature in a Razor Class Library, like the employees component that you created in the previous chapter, then you use `asp-area` to specify the feature name."
> Thanks to [Chadwick Geyser](https://github.com/chadwickgeyser) for raising this [issue on 4 December 2022](https://github.com/markjprice/cs11dotnet7/issues/6).
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:
```xml
<lidata-bs-target="#categories"data-slide-to="@c"
class="@currentItem"></li>
```
Should be `data-bs-slide-to`, as shown in the following markup:
> Thanks to [Chadwick Geyser](https://github.com/chadwickgeyser) for raising this [issue on 5 December 2022](https://github.com/markjprice/cs11dotnet7/issues/7).
In Step 1, when defining a policy for output caching, the statement uses the method `VaryByQuery`, as shown in the following code:
```cs
options.AddPolicy("views", p => p.VaryByQuery(""));
```
The method name changed in Release Candidate 2, as described [here](https://learn.microsoft.com/en-us/dotnet/core/compatibility/aspnet-core/7.0/output-caching-renames), so statement should be changed to use the new method `SetVaryByQuery`, as shown in the following code:
```cs
options.AddPolicy("views", p => p.SetVaryByQuery(""));
> Thanks to [Bob Molloy](https://github.com/BobMolloy) for raising this [issue on 19 December 2022](https://github.com/markjprice/cs11dotnet7/issues/12).
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:
> Thanks to Amer Cejudo (via email) and [Christopher Targett-Adams](https://github.com/targettadams) for raising this [issue on 20 February 2023](https://github.com/markjprice/cs11dotnet7/issues/31).
In Step 4, I tell the reader to write a statement to call an extension method that you previously created in Chapter 12, as shown in the following code:
By default, this statement registers the database context with `Scope` lifetime. This is not a problem with most ASP.NET Core projects. But in a **Blazor Server** project the `Scope` lifetime database context instance is shared between multiple threads running on the server. This can cause concurrency issues as described here:
This often only affects the SQL Server database provider but it is best to apply the code change for both SQL Server and SQLite class libraries. To fix this issue, please make the changes as shown in the following items:
# Page 733 - Building customer create, edit, and delete components
> Thanks to [Bob Molloy](https://github.com/BobMolloy) for raising this [issue on 27 December 2022](https://github.com/markjprice/cs11dotnet7/issues/15).
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:
