Your first extension method (Must know) starts off by creating the simplest form of extension methods and comparing it to the previous way of accomplishing this goal. We go into the technicalities of how the compiler handles extension methods and what they really are.

Extension methods on string data types (Must know) teaches how to extend the string data type for validation and modifications. The various caveats when working with strings are also explained.

Extension methods on classes (Should know) talks about extending your own classes or classes whose source you have no access to.

Chaining extension methods (Should know) talks about writing extension methods in a manner that allows chaining calls when using it.

Overloading extension methods (Should know) shows how to overload your own and existing extension methods.

Overriding extension methods (Should know) aims at teaching the tricks needed to override extension methods and explains its technicalities.

Extension methods on interfaces (Should know) gives examples of creating and using extension methods on interfaces with a twist to mixing it with overloading class extension methods.

Extension methods on enumerables (Should know) aims at showing many tricks of extending enumerables with modifying, filtering, and chaining.

Extension methods on IQueryable (Become an expert) aims at showing performance optimizations and tricks between IEnumerable and IQueryable.

Extension methods with generics (Become an expert) seeks to explore the caveats of extending generics. Extending generics should be done with care, and if not done properly will cause ambiguity when using them.

Extension methods with lambda expressions (Become an expert) talks about extending lambda expressions, that are somewhat of a niche feature and rarely done, and can be very useful for those familiar with the functional programming paradigm.

Structuring your project and best practices (Should know) helps the developer structure their project so it can be easily maintained.

Appendix – List of well-known extension libraries contains a list of useful extension method libraries that developers can include in their projects and get start using them immediately.

To run the code in this book you need the following:

This book is great for both new and veteran developers in C# and the .NET framework. The readers are assumed to have basic understanding of the language syntax, types, and OOP concepts. Readers are also expected to have some experience in finding their way around Visual Studio.

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text are shown as follows: "The only difference between the two code snippets is the keyword this in the first parameter."

A block of code is set as follows:

//----We use the method like this
int num = 5;
bool isNumEven = false;
//calling the extension method
isNumEven = num.IsEven();
//calling the extension method on raw values
bool isSixEven = 6.IsEven();

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "clicking the Next button moves you to the next screen".

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