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.
In Step 1, I note that the `ReadLine` method is declared to return `string?`, meaning that it could return a `null` value instead of a `string` value (including an empty one). I also note that this is treated as a warning by the compiler.
In the next edition, I will add a note to explain that this method never actually returns `null` so there is no point in checking for that in functional code. A more useful check is `string.IsNullOrEmpty` so I will add more steps to show how to use that method and `string.IsNullOrWhiteSpace` to validate text input.
In this section, I wrote about rounding rules as taught in schools and compare them to rounding rules when using C# and .NET. In schools, children are introduced to rounding rules with positive numbers and so learn the term "rounding up" and "rounding down". I did not explicitly say that for negative numbers, those terms would be reversed which can be confusing, so those terms should be avoided. This is why the .NET API uses the enum values `AwayFromZero`, `ToZero`, `ToEven`, `ToPositiveInfinity` and `ToNegativeInfinity` for improved clarity. In the next edition I will add a note about this.
At the end of this section there is a note box that explains that we could use the `C` format code to format the output as currency. If you are running on a computer in a culture that uses Euros then to show the Euro currency symbol you must enable UTF-8 encoding.
Add the following statement near the top of the code file before doing any writing to the console:
# Page 251 - Setting up a class library and console application
In Step 8, I wrote, "Run the `PeopleApp` project".
In Chapter 1, I explain how to control which project starts when a Visual Studio 2022 solution contains multiple projects by setting the startup project. In Chapters 2 to 5, I remind the reader to set the startup project.
In the 8th edition, I will add the same reminder to Chapter 6 as well, for example:
8. Set the `PeopleApp` project as the startup/active project:
This section shows how to follow best practice and treat warnings as errors. But doing so means you must write extra code in common scenarios to fix all warnings that will now be treated as errors that prevent compilation during the build process.
So this section also shows how to disable some common warnings by adding extra code. The project is NOT designed to be run. The code in it is written only to illustrate some common warnings and how to disable them to allow a build.
For example, one warning is caused by the compiler thinking there could be a null dereference. To disable the warning, you therefore need to check for a `null` value *even though we know that can never actually happen* as explained in the note. That extra code check is pointless if you run the console app and expect it to work correctly.
In the next edition, I will add another note to explicitly tell the reader not to run the project. The project implementation is not written to actually function as a check if someone has entered their name because that's not the point of this section. I will also simplify the code.
Current code:
```cs
if (name == null)
{
Console.WriteLine("You did not enter a name.");
return;
}
```
Code in next edition:
```cs
if (name == null) return; // must check for null to remove the warning
I recommend that you type from the print book or copy and paste long commands like this from the eBook into a plain text editor like Notepad. Then make sure that the whole command is properly formatted as a single line with correct spacing, before you then copy and paste it to the command-line. Copying and pasting directly from the eBook is likely to include newline characters and missing spaces and so on that break the command.
For convenience, here is the same command as a single line to make it easier to copy and paste:
# Page 547 - Creating a class library for a Northwind database context
In Step 8, you write code to implement the `OnConfiguring` method so that it sets the Filename path to the SQLite database file correctly when running in both Visual Studio 2022 and at the command-line with Visual Studio Code, as shown in the following code:
In the next edition, it will be improved in two ways. First, by defining a string value once for the database name, and second, by checking that the database file exists and throwing an exception if it does not, as shown in the following code:
> After converting the relative path to an absolute path, you can set a breakpoint to more easily see where the database file is expected to be, or add a statement to log that path.
The throwing of the exception is important because if the database file is missing, then the SQLite database provider will create an empty database file, and so if you test connecting to it, it works! But if you query it then you will see an exception related to missing tables because it does not have any tables!
On page 553, we write some unit tests for this class and for SQLite the first test seems to work even when the path is actually wrong due to this issue. By adding code to throw an exception if the database file is missing, this test will now correctly fail.
In Step 11, in the `NorthwindContextExtensions.cs` file, we should also use a dynamically constructed string for the `AddNorthwindContext` method, as shown in the following code:
```cs
public static IServiceCollection AddNorthwindContext(
# Page 551 - Creating a class library for entity models using SQL Server
In Step 14, I tell the reader, "In the `Northwind.Common.DataContext.SqlServer` project, in `NorthwindContext.cs`, remove
the compiler warning about the connection string."
It would be an improvement to also replace the hard-coded string value used for the database connection string with a dynamically constructed string using the `SqlConnectionStringBuilder` class, as shown in the following code:
```cs
// At the top of the NorthwindContext.cs file.
using Microsoft.Data.SqlClient; // SqlConnectionStringBuilder
In Step 15, in the `NorthwindContextExtensions.cs` file, we should also use a dynamically constructed string using the `SqlConnectionStringBuilder` class, as shown in the following code:
```cs
// At the top of the NorthwindContextExtensions.cs file.
using Microsoft.Data.SqlClient; // SqlConnectionStringBuilder
```
The `AddNorthwindContext` method:
```cs
public static IServiceCollection AddNorthwindContext(
this IServiceCollection services,
string? connectionString = null)
{
if (connectionString == null)
{
SqlConnectionStringBuilder builder = new();
builder.DataSource = "."; // "ServerName\InstanceName" e.g. @".\sqlexpress"
builder.InitialCatalog = "Northwind";
builder.IntegratedSecurity = true;
builder.TrustServerCertificate = true;
builder.MultipleActiveResultSets = true;
builder.ConnectTimeout = 3; // Because we want to fail fast. Default is 15 seconds.
> Note: You could also use the simpler link format `https://localhost:5001/home/category/1` but then both the action method and the view filename must be just `Category` instead of `CategoryDetail`.
