Book Image

C# 8.0 and .NET Core 3.0 – Modern Cross-Platform Development - Fourth Edition

By : Mark J. Price
Book Image

C# 8.0 and .NET Core 3.0 – Modern Cross-Platform Development - Fourth Edition

By: Mark J. Price

Overview of this book

In C# 8.0 and .NET Core 3.0 – Modern Cross-Platform Development, Fourth Edition, expert teacher Mark J. Price gives you everything you need to start programming C# applications. This latest edition uses the popular Visual Studio Code editor to work across all major operating systems. It is fully updated and expanded with new chapters on Content Management Systems (CMS) and machine learning with ML.NET. The book covers all the topics you need. Part 1 teaches the fundamentals of C#, including object-oriented programming, and new C# 8.0 features such as nullable reference types, simplified switch pattern matching, and default interface methods. Part 2 covers the .NET Standard APIs, such as managing and querying data, monitoring and improving performance, working with the filesystem, async streams, serialization, and encryption. Part 3 provides examples of cross-platform applications you can build and deploy, such as web apps using ASP.NET Core or mobile apps using Xamarin.Forms. The book introduces three technologies for building Windows desktop applications including Windows Forms, Windows Presentation Foundation (WPF), and Universal Windows Platform (UWP) apps, as well as web applications, web services, and mobile apps.
Table of Contents (21 chapters)

Querying EF Core models

Now that we have a model that maps to the Northwind database and two of its tables, we can write some simple LINQ queries to fetch data. You will learn much more about writing LINQ queries in Chapter 12, Querying and Manipulating Data Using LINQ. For now, just write the code and view the results.

  1. Open Program.cs and import the following namespaces:
    using static System.Console; 
    using Packt.Shared;
    using Microsoft.EntityFrameworkCore; 
    using System.Linq;
  2. In Program, define a QueryingCategories method, and add statements to do these tasks, as shown in the following code:
    • Create an instance of the Northwind class that will manage the database.
    • Create a query for all categories that include their related products.
    • Enumerate through the categories, outputting the name and number of products for each one.
    static void QueryingCategories()
    {
      using (var db = new Northwind())
      {
        WriteLine("Categories and how many products they have:");
        ...