Book Image

Learn C# Programming

By : Marius Bancila, Raffaele Rialdi, Ankit Sharma
5 (1)
Book Image

Learn C# Programming

5 (1)
By: Marius Bancila, Raffaele Rialdi, Ankit Sharma

Overview of this book

The C# programming language is often developers’ primary choice for creating a wide range of applications for desktop, cloud, and mobile. In nearly two decades of its existence, C# has evolved from a general-purpose, object-oriented language to a multi-paradigm language with impressive features. This book will take you through C# from the ground up in a step-by-step manner. You'll start with the building blocks of C#, which include basic data types, variables, strings, arrays, operators, control statements, and loops. Once comfortable with the basics, you'll then progress to learning object-oriented programming concepts such as classes and structures, objects, interfaces, and abstraction. Generics, functional programming, dynamic, and asynchronous programming are covered in detail. This book also takes you through regular expressions, reflection, memory management, pattern matching, exceptions, and many other advanced topics. As you advance, you'll explore the .NET Core 3 framework and learn how to use the dotnet command-line interface (CLI), consume NuGet packages, develop for Linux, and migrate apps built with .NET Framework. Finally, you'll understand how to run unit tests with the Microsoft unit testing frameworks available in Visual Studio. By the end of this book, you’ll be well-versed with the essentials of the C# language and be ready to start creating apps with it.
Table of Contents (20 chapters)

The Dictionary<TKey, TValue> collection

A dictionary is a collection of key-value pairs that allows fast lookup based on a key. Adding, searching, and deleting an item are very fast operations and are performed in O(1). The exception here is adding a new value if the capacity must be increased, in which case it becomes O(n).

In .NET, the generic Dictionary<TKey,TValue> class implements a dictionary. TKey represents the type of the key and TValue represents the type of the value. The elements of the dictionary are KeyValuePair<TKey,TValue> objects.

Dictionary<TKey, TValue> has several overloaded constructors that allow us to create an empty dictionary or a dictionary filled with some initial values. The default constructor of this class will create an empty dictionary. Take a look at the following code snippet:

var languages = new Dictionary<int, string>(); 

Here, we are creating an empty dictionary called languages that has a key of the int...