Professional C# 5.0 and .NET 4.5.1

Chapter 8Delegates, Lambdas, and Events

WHAT’S IN THIS CHAPTER?

• Delegates
• Lambda expressions
• Closures
• Events
• Weak Events

WROX.COM CODE DOWNLOADS FOR THIS CHAPTER

The wrox.com code downloads for this chapter are found at www.wrox.com/go/procsharp on the Download Code tab. The code for this chapter is divided into the following major examples:

• Simple Delegates
• Bubble Sorter
• Lambda Expressions
• Events Sample
• Weak Events

REFERENCING METHODS

Delegates are the .NET variant of addresses to methods. Compare this to C++, where a function pointer is nothing more than a pointer to a memory location that is not type-safe. You have no idea what a pointer is really pointing to, and items such as parameters and return types are not known. This is completely different with .NET; delegates are type-safe classes that define the return types and types of parameters. The delegate class not only contains a reference to a method, but can hold references to multiple methods.

Lambda expressions are directly related to delegates. When the parameter is a delegate type, you can use a lambda expression to implement a method that’s referenced from the delegate.

This chapter explains the basics of delegates and lambda expressions, and shows you how to implement methods called by delegates with lambda expressions. It also demonstrates how .NET uses delegates as the means of implementing events.

DELEGATES

Delegates exist for situations in which you want to pass methods around to other methods. To see ...