Book Image

C# 7.1 and .NET Core 2.0 ??? Modern Cross-Platform Development - Third Edition

By : Mark J. Price
Book Image

C# 7.1 and .NET Core 2.0 ??? Modern Cross-Platform Development - Third Edition

By: Mark J. Price

Overview of this book

C# 7.1 and .NET Core 2.0 – Modern Cross-Platform Development, Third Edition, is a practical guide to creating powerful cross-platform applications with C# 7.1 and .NET Core 2.0. It gives readers of any experience level a solid foundation in C# and .NET. The first part of the book runs you through the basics of C#, as well as debugging functions and object-oriented programming, before taking a quick tour through the latest features of C# 7.1 such as default literals, tuples, inferred tuple names, pattern matching, out variables, and more. After quickly taking you through C# and how .NET works, this book dives into the .NET Standard 2.0 class libraries, covering topics such as packaging and deploying your own libraries, and using common libraries for working with collections, performance, monitoring, serialization, files, databases, and encryption. The final section of the book demonstrates the major types of application that you can build and deploy cross-device and cross-platform. In this section, you'll learn about websites, web applications, web services, Universal Windows Platform (UWP) apps, and mobile apps. By the end of the book, you'll be armed with all the knowledge you need to build modern, cross-platform applications using C# and .NET.
Table of Contents (31 chapters)
Title Page
Credits
About the Author
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface
2
Part 1 – C# 7.1
8
Part 2 – .NET Core 2.0 and .NET Standard 2.0
16
Part 3 – App Models
22
Summary
Index

Casting within inheritance hierarchies


Casting is subtly different from converting between types.

Implicit casting

In the previous example, you saw how an instance of a derived type can be stored in a variable of its base type (or its base's base type, and so on). When we do this, it is called implicit casting.

Explicit casting

Going the other way is an explicit cast, and you must use parentheses to do it.

In the Main method, add the following code:

Employee e2 = aliceInPerson; 

Visual Studio 2017 and Visual Studio Code display a red squiggle and a compile error in the Error List and Problems windows, as shown in the following screenshot:

Change the code as follows:

Employee e2 = (Employee)aliceInPerson; 

Handling casting exceptions

The compiler is now happy; but, because aliceInPerson might be a different derived type, like Student instead of Employee, we need to be careful. This statement might throw an InvalidCastException error.

We can handle this by writing a try statement, but there is a better...