Add item for page 454

docs/errata/README.md

@@ -2,7 +2,7 @@
 
 If you find any mistakes in the seventh edition, *C# 11 and .NET 7 - Modern Cross-Platform Development Fundamentals*, or if you have suggestions for improvements, then please [raise an issue in this repository](https://github.com/markjprice/cs11dotnet7/issues) or email me at markjprice (at) gmail.com.
 
-[**Errata** (38 items)](errata.md): Typos, tool user interface changes, or mistakes in code that would cause a compilation error that prevents a successful build.
+[**Errata** (39 items)](errata.md): Typos, tool user interface changes, or mistakes in code that would cause a compilation error that prevents a successful build.
 
 [**Improvements** (26 items)](improvements.md): Changes to text or code that would improve the content. These are optional.
 

docs/errata/errata.md

@@ -1,4 +1,4 @@
-**Errata** (38 items)
+**Errata** (39 items)
 
 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.
 
@@ -35,6 +35,9 @@ If you find any mistakes, then please [raise an issue in this repository](https:
 - [Page 399 - Managing directories](#page-399---managing-directories)
 - [Page 362 - Joining, formatting, and other string members](#page-362---joining-formatting-and-other-string-members)
 - [Page 412 - Compressing streams](#page-412---compressing-streams)
+- [Page 454 - Scaffolding models using an existing database](#page-454---scaffolding-models-using-an-existing-database)
+  - [Category class changes](#category-class-changes)
+  - [NorthwindDb class changes](#northwinddb-class-changes)
 - [Page 477 - Inserting entities](#page-477---inserting-entities)
 - [Page 548 - Creating a class library for a Northwind database context](#page-548---creating-a-class-library-for-a-northwind-database-context)
 - [Page 551 - Creating a class library for entity models using SQL Server](#page-551---creating-a-class-library-for-entity-models-using-sql-server)
@@ -465,6 +468,88 @@ It should be:
 WriteLine("The compressed contents:");
 ```
 
+# 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; }
+```
+
 # Page 477 - Inserting entities
 
 > Thanks to [Chadwick Geyser](https://github.com/chadwickgeyser) for raising this [issue on 29 November 2022](https://github.com/markjprice/cs11dotnet7/issues/5).