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Errata (50 items)

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

Warning! Avoid copying and pasting links that break over multiple lines and include hyphens or dashes because your PDF reader might remove a hyphen thinking that it being helpful but break the link! Just click on the links and they will work. Or carefully check that your PDF reader has not removed a hyphen after pasting into your web browser address bar. See an example of this issue here.

Page 15 - Central Package Management

Thanks to Rob for raising this issue on December 26, 2024.

Packt publishes Early Access editions of some of their books. They are available on the website via Packt subscription. The content uses preliminary drafts of books that will change during the writing and editing process. Once the final version is signed off by author and publisher, the paperback, Kindle, and other ebook formats are produced. The final step is to update the Early Access online web edition to match the published edition but sometimes this process takes up to a week after publish date.

In the Early Access edition of this book, Chapter 1 included the following package versions for testing in the Directory.Packages.props file:

<ItemGroup Label="For unit testing.">
  <PackageVersion Include="coverlet.collector" Version="6.0.2" />
  <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.0.0" />
  <PackageVersion Include="xunit" Version="2.9.0" />
  <PackageVersion Include="xunit.runner.visualstudio" Version="3.0.0" />
</ItemGroup>

But in the final published editions they are as shown in the following markup:

<ItemGroup Label="For testing.">
  <PackageVersion Include="coverlet.collector" Version="6.0.2" />
  <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
  <PackageVersion Include="xunit" Version="2.9.2" />
  <!--The following package was still a preview on .NET 9 release day.-->
  <PackageVersion Include="xunit.runner.visualstudio" Version="3.0.0-pre.49" />
  <PackageVersion Include="Microsoft.Playwright" Version="1.49.0" />
  <PackageVersion Include="Microsoft.AspNetCore.Mvc.Testing" Version="9.0.0" />
</ItemGroup>

And remember to check if a newer package version has been released. For example, the Microsoft.NET.Test.Sdk package is already now 17.12.0, so I updated the solution code in the book's GitHub repository.

Page 19 - Making good use of the GitHub repository for this book

Thanks to JohnMaz1031 for raising this issue on September 13, 2025.

The Good Practice box has an invalid link that ends with a double file extension .md.md: https://github.com/markjprice/web-dev-net9/blob/main/docs/errata/README.md.md. It should be: https://github.com/markjprice/web-dev-net9/blob/main/docs/errata/README.md

Page 23 - Installing Docker and the Azure SQL Edge container image

Thanks to P9avel for raising this issue on January 2, 2025.

In the paragraph that leads in to the numbered steps, I wrote, "Azure SQL Edge requires a 64-bit processor (either x64 or ARM64), with a minimum of one processor and 1 GB RAM on the host:"

In the next edition, I will simplify that statement to the following, "Azure SQL Edge requires a 64-bit processor (either x64 or ARM64), with a minimum of 1 GB RAM on the host:"

Page 33 - Creating a class library for entity models

Thanks to P9avel for raising this issue on January 2, 2025.

In the Good Practice box, I use the phrase "data context". In other places, I use the phrase "database context". Both uses refer to a class that derives from DbContext that represents a combination of the Unit Of Work and Repository patterns such that it can be used to query from a database and group together changes that will then be written back to the store as a unit.

The Microsoft official documentation just uses the word "context" when referring to this class but I feel that loses some meaning. In future editions, I will try to consistently use the phrase "database context".

Page 67 - What does UseMigrationsEndPoint do?

Thanks to P9avel for raising this issue on January 3, 2025.

This section is about trying to find out what path is configured as an endpoint when you call the UseMigrationsEndPoint extension method. We already know what calling the UseMigrationsEndPoint extension method does conceptually: it configures a route that if called, triggers a database migration. What we don't know is what the relative path is for that route.

In the fourth paragraph, I wrote, "You can find the source code for the UseMigrationsEndPoint extension method at the following link: https://github.com/dotnet/aspnetcore/blob/main/src/Middleware/Diagnostics.EntityFrameworkCore/src/MigrationsEndPointOptions.cs#L18."

But we do not care about the source code for the UseMigrationsEndPoint extension method itself. We just want to know the relative path that it uses for its endpoint.

So the link is correct, because it shows us what the path is defined by a property on the MigrationsEndPointOptions class named DefaultPath. But the description is misleading. In the next edition I will write, "You can find the source code for the relative path used by the UseMigrationsEndPoint extension method at the following link: https://github.com/dotnet/aspnetcore/blob/main/src/Middleware/Diagnostics.EntityFrameworkCore/src/MigrationsEndPointOptions.cs#L18."

Page 76 - View model example, Page 274 - Reviewing the default endpoint routing configuration

Thanks to Moisés Sirvente for raising this issue on May 14, 2025.

In the third paragraph, I wrote, "The code in the GitHub repository solution and below uses SQLite, but you can easily use SQL Server if you prefer." I should have written, "The code in the GitHub repository solution and below uses SQL Server."

In Table 8.1, in the last row for the AddNorthwindContext entry, I wrote, "A custom extension method we created to make it easier to register the NorthwindContext class for either SQLite or SQL Server based on the project referenced." I should have written, "A custom extension method we created to make it easier to register the NorthwindContext class for SQL Server."

Page 81 - Implementing views

Thanks to P9avel for raising this issue on January 3, 2025.

At the end of Step 9, I wrote, "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 originally planned to have sections about view components and Razor class libraries but they were postponed to the next edition. If I do add those sections and have a task that creates an employees component, then I will be able to leave this sentence unchanged. Otherwise, I will change it to, "If you want to navigate to a feature in a Razor class library then you use asp-area to specify the feature name."

Page 83 - How cache busting with Tag Helpers works

Thanks to P9avel for raising this issue on January 3, 2025.

The path in the <script> element has an extra space, as shown in the following markup:

<script src="~/js/site.js? v=Kl_dqr9NVtnMdsM2MUg4qthUnWZm5T1fCEimBPWDNgM"></
script>

In the next edition, I will delete the extra space, as shown in the following markup:

<script src="~/js/site.js?v=Kl_dqr9NVtnMdsM2MUg4qthUnWZm5T1fCEimBPWDNgM"></
script>

Page 97 - Temporarily storing data

Thanks to P9avel for raising this issue on January 3, 2025.

In Step 2, I wrote, "(You will learn more about middleware later in this chapter.)" But during final drafts of the book, I moved this section from Chapter 8 to Chapter 2, so this note is no longer true. In the next edition, I will delete the note, and I will add a new section briefly introducing middleware and other terminology to Chapter 1.

Page 110 - Model binders in detail

Thanks to Moisés Sirvente for raising this issue on May 23, 2025.

Figure 3.2 should not show the <input> element containing the value 1 because that is added to the form later, and it should show the value 3 in the output for Model.Thing.Id because at this point, it is set from the query string: ?id=3.

Page 110 - Passing a route parameter, Page 111 - Passing a form parameter

Thanks to Moisés Sirvente for raising this issue on May 23, 2025 and this issue on May 23, 2025.

In Step 3, I should have written "click Model Binding" not just "click Binding".

Page 117 - Displaying Northwind suppliers

Thanks to P9avel for raising this issue on January 4, 2025.

In Step 5, I show the reader how to render the links to edit and delete a supplier using simple anchor tags (and with the wrong path!), as shown in the following markup:

<a href="edit/@s.SupplierId">Edit</a>
<a href="delete/@s.SupplierId">Delete</a>

But the links should be rendered using the Anchor Tag Helper to make it clearer, as shown in the following markup:

<a asp-controller="Home" asp-action="EditSupplier"
   asp-route-id="@s.SupplierId">Edit</a>
<a asp-controller="Home" asp-action="DeleteSupplier"
   asp-route-id="@s.SupplierId">Delete</a>

I also forgot to add the markup for the Add New Supplier button that should appear between the Suppliers heading and the table of suppliers, as shown in the following markup:

<h1 class="display-2">Suppliers</h1>
<a class="btn btn-outline-primary"
   asp-controller="Home" asp-action="AddSupplier">Add New Supplier</a>
<table class="table">

The markup was already correct in the code solution found here: https://github.com/markjprice/web-dev-net9/blob/main/code/MatureWeb/Northwind.Mvc/Views/Home/Suppliers.cshtml

Page 117 - Displaying Northwind suppliers

Thanks to Moisés Sirvente for raising this issue on May 28, 2025.

In Step 6, I wrote, "after the Home navigation menu item" when I should have written "after the Model Binding navigation menu item". The code for this step should also show the Model Binding menu item instead of the Home menu item.

Page 118 - Inserting, updating, and deleting suppliers

Thanks to P9avel for raising this issue on January 4, 2025.

In Step 5, the first bullet says, "The <form> element with a PUT method is ordinary HTML, so an <input type="submit" /> element inside it will make an HTTP PUT request back to the current path with values of any other elements inside that form."

But HTML forms inherently support only two HTTP methods: GET and POST. They do not natively support PUT, DELETE, or other HTTP methods. This limitation means that when you need to use PUT or DELETE, you cannot specify these methods directly in the <form> element.

A convention in ASP.NET Core MVC is to simulate these methods using POST, often with the help of a hidden input field called _method or specifying the action in the path, like /home/editsupplier and /home/deletesupplier.

In the next edition, I will change PUT to POST in that sentence, and I will add a note at the start of this section to explain why we do not use PUT or DELETE methods, despite in a RESTful API design:

  • POST is typically used for creating resources.
  • PUT is used for updating resources.
  • DELETE is used for deleting resources.

Page 129 - Querying a database and using display templates

Thanks to Paul Marangoni for raising this issue on March 3, 2025.

In Step 3, I tell the reader to modify the contents of CostlyProducts.cshtml. But two of the column values for category name and supplier company name do not output because of missing @ before Html. The correct statements should be as shown in the following markup:

@foreach (Product p in Model)
{
  <tr>
    <td>
      @if (p.Category is not null) { @Html.DisplayFor(modelItem => p.Category.CategoryName); }
    </td>
    <td>
      @if (p.Supplier is not null) { @Html.DisplayFor(modelItem => p.Supplier.CompanyName); }
    </td>

Or you can use block style, as I use in the code solution for this file, as shown in the following markup:

@foreach (Product p in Model)
{
  <tr>
    <td>
      @if (p.Category is not null) 
      { 
        @Html.DisplayFor(modelItem => p.Category.CategoryName); 
      }
    </td>
    <td>
      @if (p.Supplier is not null) 
      { 
        @Html.DisplayFor(modelItem => p.Supplier.CompanyName); 
      }
    </td>

Page 134 - Practice implementing MVC by implementing a category detail page

Thanks to Moisés Sirvente for raising this issue on June 4, 2025.

In the view, the label for the category name says "Product Name", as shown in the following markup:

<dt>Product Name</dt>
<dd>@Model.CategoryName</dd>

It should be "Category Name", as shown in the following markup:

<dt>Category Name</dt>
<dd>@Model.CategoryName</dd>

Page 143 - Comparing HTML Helpers and Tag Helpers

Thanks to P9avel for raising this issue on January 5, 2025.

I showed two examples of rendering a hyperlink:

@Html.ActionLink("View our privacy policy.", "Privacy", "Index")

@Html.ActionLink(linkText: "View our privacy policy.",
  action: "Privacy", controller: "Index")

But the controller name is Home, not Index, so the markup should be:

@Html.ActionLink("View our privacy policy.", "Privacy", "Home")

@Html.ActionLink(linkText: "View our privacy policy.",
  action: "Privacy", controller: "Home")

Page 153 - Exploring the Environment Tag Helper

Thanks to Donald Maisey for raising this issue on May 30, 2025.

In Step 6, I tell the reader to "change the environment setting to Production". But we are using MapStaticAssets to compress stylesheets and other static files, and the system looks in different paths between Development and Production. Since we are actually still running the development build of the project, the paths do not match and you will lose all styling.

To fix the issue, we need to manually tell the static asset system to read the current environment so it knows to use the Production paths even though we are not running the production build. (Or we could use dotnet publish and then run the build from the publish directory which is effectively what happens in the real-world: you run the production build with production configuration.)

In the next edition, I will add a few steps:

  1. In Program.cs, import the namespace for manually configuring static assets, as shown in the following code:
// To use StaticWebAssetsLoader.
using Microsoft.AspNetCore.Hosting.StaticWebAssets;
  1. In Program.cs, after creating the builder, configure static assets to read the current environment from configuration, as shown in the following code:
// Enable switching environments (Development, Production) during development.
StaticWebAssetsLoader.UseStaticWebAssets(
  builder.Environment, builder.Configuration);

Page 154 - Exploring Forms-related Tag Helpers

Thanks to a reader who emailed a question about this issue to Packt.

In Step 1, I told the reader to enter markup for two forms. The second form uses the Label Tag Helper, but the <label> elements I used were self-closing, as shown in the following markup:

<label asp-for="ShipperId" class="form-label" />

Self-closing tags are not supported by the Label Tag Helper. You must use a pair of open and close tags, as shown in the following markup:

<label asp-for="ShipperId" class="form-label"></label>

The complete corrected second form is shown in the following markup:

<h2>With Form Tag Helper</h2>
<form asp-controller="Home" asp-action="ProcessShipper"
      class="form-horizontal" role="form">
  <div>
    <div class="mb-3">
      <label asp-for="ShipperId" class="form-label"></label>
      <input asp-for="ShipperId" class="form-control">
    </div>
    <div class="mb-3">
      <label asp-for="CompanyName" class="form-label"></label>
      <input asp-for="CompanyName" class="form-control">
    </div>
    <div class="mb-3">
      <label asp-for="Phone" class="form-label"></label>
      <input asp-for="Phone" class="form-control">
    </div>
    <div class="mb-3">
      <input type="submit" class="form-control">
    </div>
  </div>
</form>

Also, the Label Tag Helper will use the property names from the model as the labels in the form, so it will use ShipperId and CompanyName by default.

To override these values, in the Northwind.EntityModels project, in the Shipper.cs class, you can decorate the properties with the [Display] attribute, as shown in the following code:

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using Microsoft.EntityFrameworkCore;

namespace Northwind.EntityModels;

public partial class Shipper
{
  [Key]
  [Display(Name = "Shipper ID")] // Used by the Label Tag Helper.
  public int ShipperId { get; set; }

  [StringLength(40)]
  [Display(Name = "Company Name")] // Used by the Label Tag Helper.
  public string CompanyName { get; set; } = null!;

  [StringLength(24)]
  public string? Phone { get; set; }

  [InverseProperty("ShipViaNavigation")]
  public virtual ICollection<Order> Orders { get; set; } = new List<Order>();
}

This fix also affects Step 5, when the reader must View page source and review the generated HTML. For example, in the book, the first label renders as <label class="form-label" for="ShipperId" />, but after applying the fix, it will render as <label class="form-label" for="ShipperId">Shipper ID</label>.

Page 158 - Localizing your user interface

Thanks to P9avel for raising this issue on January 5, 2025.

I wrote, "In the coding task, you will create a console app with an embedded invariant culture and satellite assemblies for Danish, French, French-Canadian, Polish, and Iranian (Persian)."

I should have written, "In the coding task, you will add resources to the ASP.NET Core MVC project that compile to an embedded invariant culture (English) and satellite assemblies for French (Neutral), French (France), and English (British)."

Page 159 - If you are using Visual Studio

Thanks to P9avel for raising this issue on January 5, 2025.

Figure 4.6 to Figure 4.9 all show the Orders.resx file in a folder structure: Resources\Views\Orders but they should be Resources\Views\Home.

In the next edition, I will retake or edit the screenshots to show the correct folder name Home.

Also, in Step 1, the path says Resource\Views\Home when it should be Resources\Views\Home.

Page 160 - If you are using Visual Studio

Thanks to Paul Marangoni for raising this issue on March 5, 2025.

Throughout this section, I repeatedly write Index when I should have written Orders. For example, in Step 5, I wrote, "Copy and paste the file and rename it Index.en-GB.resx." I should have written, "Copy and paste the file and rename it Orders.en-GB.resx."

Similarly in Steps 6, 8, 9, 10, and 11.

Page 161 - If you are using VS Code

Thanks to P9avel for raising this issue on January 5, 2025.

In Step 1, I wrote, "In Resources\Views\Orders, add a new file named Index.resx." This should be, "In Resources\Views\Home, add a new file named Orders.resx."

Similarly in Steps 3, 4, 5, 6, 7, and 8.

Page 162 - If you are using VS Code

Thanks to P9avel for raising this issue on January 5, 2025.

In Step 6, I wrote, "modify the value column", when I should have written, "modify the value element".

Page 163 - Other resource file tools

Thanks to P9avel for raising this issue on January 5, 2025.

I wrote, "...without needing to recompile the original console app." I should have written, "...without needing to recompile the original project."

Page 167 - Understanding the Accept-Language header

Thanks to Paul Marangoni for raising this issue on March 5, 2025.

In the third bullet point, I wrote, "fr-FR;q=0.8: English language in France ranked at 0.8"

I should have written, "fr-FR;q=0.8: French language in France ranked at 0.8"

Page 208 - Exploring in-memory object caching

Thanks to P9avel for raising this issue on January 6, 2025.

In Step 5, I wrote, "add statements to try to get the product from the cache, and if it is not cached, get it from the database and set it in the cache, using a sliding expiration of one hour". The sliding expiration should be five seconds, to match the code: SlidingExpiration = TimeSpan.FromSeconds(5).

In Step 9, I wrote, "Click Reload this page within 30 seconds", but this should be "5 seconds".

In Step 10, I wrote, "Wait at least 30 seconds", but this should be "5 seconds".

In Step 11, I wrote, "within the 30-second sliding expiration window", but this should be "5-second".

In the next edition, I might change the duration to ten seconds to give readers more time to review the console output and click reload.

Page 211 - Caching objects using distributed caching

Thanks to Paul Marangoni for raising this issue on March 11, 2025.

In Step 3, the code shows a constructor named ProductsController with a logger parameter of type ILogger<ProductsController>, as shown in the following code:

public ProductsController(ILogger<ProductsController> logger,

It should be a constructor named HomeController with a logger parameter of type ILogger<HomeController>, as shown in the following code:

public HomeController(ILogger<HomeController> logger,

Page 213 - Caching objects using distributed caching

Thanks to Moisés Sirvente for raising this issue on August 26, 2025.

In Step 8, I wrote "Click Reload this page within five seconds," when I should have written "Click Reload this page within one minute".

Page 267 - When you cannot use constructor injection

Thanks to P9avel for raising this issue on January 7, 2025.

For the Background services bullet, I ended with the sentence, "The solution is to use method injection by resolving services within the ExecuteAsync method."

I should have written, "The solution is to create a scope with the IServiceScopeFactory.CreateScope() API, as described in the following link: https://learn.microsoft.com/en-us/dotnet/core/extensions/scoped-service."

Page 295 - Configuration validation

Thanks to P9avel for raising this issue on January 9, 2025.

In this section, I wrote, "ASP.NET Core allows you to validate configuration options. This can be done by implementing the IValidateOptions<T> interface or using the Validate extension method, as shown in the following code:

builder.Services
  .Configure<NorthwindOptions>(builder.Configuration.GetSection("Northwind"))
  .Validate(settings => settings.PagerSize > 0,
  "PagerSize must be greater than zero.");

But to use the Validate extension method, you must call the AddOptions<T> method, as shown in the following code:

builder.Services
  .AddOptions<NorthwindOptions>("Northwind")
  .Validate(settings => settings.PagerSize > 0,
  "PagerSize must be greater than zero.");

Page 304 - Adding Aspire to an existing solution

Thanks to Moisés Sirvente for raising this issue on November 26, 2025.

In Steps 8 and 10, I wrote, "In the Northwind.Mvc.csproj project file, in Program.cs, ..." when I should have written, In the Northwind.Mvc project, in Program.cs, ...

Page 307 - Adding Aspire to an existing solution

Thanks to P9avel for raising this issue on January 9, 2025.

In Step 11, I wrote that I had highlighted the code but the highlight is missing. In the next edition, I will highlight the following code statement:

IResourceBuilder<ContainerResource> sqlServer = builder
  .AddContainer(name: "azuresqledge",
  image: "mcr.microsoft.com/azure-sql-edge")
  .WithLifetime(ContainerLifetime.Persistent);

And the following additional method call after adding the project: .WaitFor(sqlServer).

Page 308 - Adding Aspire to an existing solution

Thanks to P9avel for raising this issue on January 9, 2025.

In Step 14, the output shown is from a different project solution. You can tell because: (1) the version of Aspire is 8.0, (2) the host directory is the Microsoft eShop sample web project, and (3) the port number is different.

In the next edition, I will replace this output with the correct output for the MatureWeb solution.

Page 337 - Configuring the customer repository and Web API controller

Thanks to P9avel for raising this issue on January 11, 2025.

In Step 9, the RetrieveAsync method should have the default value passed to it, but instead I accidently put that in the GetCustomer method declaration, as shown in the following code:

public async Task<IActionResult> GetCustomer(string id, default)
{
  Customer? c = await _repo.RetrieveAsync(id);

It should be as shown in the following code:

public async Task<IActionResult> GetCustomer(string id)
{
  Customer? c = await _repo.RetrieveAsync(id, default);

The code was already correct in the GitHub respository: https://github.com/markjprice/web-dev-net9/blob/main/code/MatureWeb/Northwind.WebApi/Controllers/CustomersController.cs#L47

Page 346 - Understanding the OpenAPI Specification

Thanks to Paul Marangoni for raising this issue on March 31, 2025.

In Step 4, I wrote "using Swagger" when I should have written "mapping an endpoint for an auto-generated OpenAPI document".

Page 350 - Caching HTTP responses for web services

Thanks to Paul Marangoni for raising this issue on March 31, 2025.

In Table 9.5, in the no-cache row, I wrote "A server is telling the client and intermediaries not the cache the response." I should have written "A server is telling the client and intermediaries not to cache the response."

Page 366 - Configuring HTTP logging for the web service

Thanks to Paul Marangoni for raising this issue on April 3, 2025.

In Step 5, I wrote, "In the Views/Tools folder" when I should have written, "In the Views/Cors folder".

Page 367 - Configuring HTTP logging for the web service

Thanks to Paul Marangoni for raising this issue on April 3, 2025.

In Step 6, the code for the getCustomersButton_click event handler function looks in the input box named companyName, as shown in the following code:

function getCustomersButton_click() { 
  xhr.open("GET", baseaddress + "api/customers/?country=" + 
    document.getElementById("companyName").value); 
    
  xhr.send(); 
}

It should look in the input box named country, as shown in the following code:

function getCustomersButton_click() { 
  xhr.open("GET", baseaddress + "api/customers/?country=" + 
    document.getElementById("country").value); 
    
  xhr.send(); 
}

Page 381 - Summary

Thanks to Moisés Sirvente for raising this issue on March 9, 2026.

The second bullet says "Swagger" when it should say "OpenAPI". This has already been fixed in the 2nd edition.

Page 399 - Creating an HTTP file for making requests

Thanks to P9avel for raising this issue on January 11, 2025.

In Step 4, in Table 10.2, the last row has a column value of products(2) for the Relative request. It should be products(77) because the Response column value is product 77.

Page 410 - Enabling entity inserts, updates, and deletes

Thanks to Paul Marangoni for raising this issue on April 28, 2025.

In Step 9, I wrote, "Optionally, implement two more methods to enable updates using an HTTP PUT request and deletes using an HTTP DELETE request." Although the solution code for the delete method works, the code for the update method fails with an error message: 405 Method Not Allowed.

This is because the method signature I provided does not match the required signature. Here's the failing solution method signature:

public IActionResult Put([FromBody] Product product)

The preceding method is missing a parameter that must be named key and that has the data type of the primary key. For the Products table, this must be int, and then that value should be used to find the existing Product entity to update, as shown in the following code:

public IActionResult Put(int key, [FromBody] Product product)
{
  Product? productToUpdate = _db.Products.Find(key);

  if (productToUpdate is null)
  {
    return NotFound($"Product with id {key} not found.");
  }

  productToUpdate.ProductName = product.ProductName;
  productToUpdate.SupplierId = product.SupplierId;
  productToUpdate.CategoryId = product.CategoryId;
  productToUpdate.QuantityPerUnit = product.QuantityPerUnit;
  productToUpdate.UnitPrice = product.UnitPrice;
  productToUpdate.UnitsInStock = product.UnitsInStock;
  productToUpdate.UnitsOnOrder = product.UnitsOnOrder;
  productToUpdate.ReorderLevel = product.ReorderLevel;
  productToUpdate.Discontinued = product.Discontinued;

  _db.SaveChanges();
  return Updated(product);
}

You will also need to pass the key value when you call the service, using either products/78 or products(78), as shown in the following code:

### Update an existing product.
PUT {{base_address}}products/78
Content-Type: application/json

{
  "ProductId": 78,
  "ProductName": "Impossible Burger",
  "SupplierId": 7,
  "CategoryId": 6,
  "QuantityPerUnit": "Pack of 4",
  "UnitPrice": 50.25,
  "UnitsInStock": 50,
  "UnitsOnOrder": 0,
  "ReorderLevel": 30,
  "Discontinued": false
}

Warning! Change the value of the primary key 78 to match the value of the new product that you previous inserted if necessary.

I will also add more explanation of how conventions are used by the OData system to decide which HTTP methods to allow based on which method signatures are provided by the controller class.

Page 411 - Calling services in the Northwind MVC website

Thanks to P9avel for raising this issue on January 11, 2025.

In Step 1, I wrote, "add a navigation menu item to go to a CORS controller with a JavaScript action method".

I should have written, "add a navigation menu item to go to a ODataClient controller with an Index action method".

Page 458 - Mocking with NSubstitute example

Thanks to Paul Marangoni for raising this issue on May 7, 2025.

In Step 2, I wrote "treat errors as errors" when I should have written "treat warnings as errors".

Page 460 - Mocking with NSubstitute example

Thanks to Moisés Sirvente for raising this issue, this issue, and this issue on April 21, 2026.

In Step 8, I wrote, "in the Chapter11 folder", when I should have written, "in the MatureWeb folder".

Before Step 10, there should be an extra step to remove the version numbers from the project file:

<PackageReference Include="coverlet.collector" />
<PackageReference Include="Microsoft.NET.Test.Sdk" />
<PackageReference Include="xunit" />
<PackageReference Include="xunit.runner.visualstudio" />

Before Step 11, we need to define the NSubstitute package version in the file Directory.Packages.props:

<PackageVersion Include="NSubstitute" Version="5.3.0" />

Thanks to P9avel for raising this issue on January 13, 2025.

In Step 11, I wrote, "In the BusinessLogicUnitTests project, add a package reference for NSubstitute, as shown in the following markup:

<PackageReference Include="NSubstitute" Version="5.1.0" />

But we are using CPM, so you should not specify the version number, as shown in the following markup:

<PackageReference Include="NSubstitute" />

Page 485 - Creating and initializing a new Umbraco project

Thanks to P9avel for raising this issue on January 14, 2025.

In the note box at the end of this section, I wrote, "The relative path to the Umbraco backoffice for your website is /umbraco. So, the absolute link to the website will be https://localhost:5131/ and the absolute link to the website will be https://localhost:5131/umbraco."

I mistakenly repeated, "the absolute link to the website", so I should have written, "The relative path to the Umbraco backoffice for your website is /umbraco. So, the absolute link to the website will be https://localhost:5131/ and the absolute link to the Umbraco backoffice will be https://localhost:5131/umbraco."

And I had previously written a note box before Step 17, "The Umbraco backoffice is accessed through the /umbraco relative path, so for our project, it is at the following link: https://localhost:5131/umbraco."

In the next edition, I will remove one of these note boxes. I will also add a heading between steps 7 and 8 to break up this long task a bit more.

Page 491 - Setting up languages, Page 495 - Adding a home page as content

Thanks to Paul Marangoni for raising this issue on May 14, 2025 and discovering why and how to fix it.

In this section, I tell the reader to configure three languages: US English, British English, and French. But this causes an issue later when the reader tries to publish because the Title property is mandatory and the French language does not have a fallback.

On page 491, after Step 8, I will add some notes to highlight:

  • English (United States) is the default language.
  • English (United Kingdom) will fall back to using English (United States) if Umbraco cannot find a UK version of content.
  • French will NOT fall back to English (United States) so we MUST supply values for mandatory properties like Title or publishing will fail.

On page 495, in Steps 4 and 5, I tell the reader to enter a Title and other properties for English (United States). In Step 6 I tell the reader to save and publish, but it will give an error because I skipped a step to set a Title for the French variation of the page.

In the next edition, I will add a step before Step 6 to tell the reader to click the language selector at the top of the page and change to French language, and then enter values for the Title in French. (These steps are in the book but later in page 498 in Steps 9 and 10 so I will move them earlier.)

Page 497 - Configuring the French variant home page

Thanks to zkazz for raising this issue on March 20, 2026.

The user interface labelling has changed. In Steps 3 and 5, I wrote, "In the Domains section, click Add new domain."

This should now be, "In the Hostnames section, click Add new hostname.", as shown in the following figure: Configuring hostnames

Page 513 - Global settings

Thanks to Donald Maisey for raising this issue on July 3, 2025.

The first sentence says, "The options in the security section..."

This should have said, "The options in the global section..."