Learning C# 3.0

Summary

• Modern GUIs rely on events generated by the user or by the system to know what action to take.

• A delegate is a reference to a method of a particular signature and return type.

• Delegates allow polymorphism by encapsulating a method that matches the delegate signature. The method encapsulated by the delegate is decided at runtime.

• An object can publish a series of events to which other classes can subscribe. The publishing class defines a delegate and an event based on that delegate. The subscribing class creates a method that matches the signature of the delegate, and registers that method with an instance of the delegate.

• In .NET, all event handlers return void, and take two parameters. The first parameter is of type object and is the object that raises the event; the second argument is an object of type EventArgs or of a type derived from EventArgs, which may contain useful information about the event.

• Event handlers subscribe to delegates using the += operator and unsubscribe using the -= operator.

• The keyword event ensures that event handlers can only subscribe or unsubscribe to the event. Handlers can’t call the delegate event directly, nor can they access its internal members.

• Instead of passing a method name to a delegate, you can pass a block of code, using the keyword delegate. This creates an anonymous method.

• A lambda expression is an expression using the operator => that returns an unnamed method. Lambda expressions are similar to anonymous methods, but aren’t restricted ...