Free-ebooks-library - Bahar Ali Khan

4
Advanced C#
In this chapter, we cover advanced C# topics that build on concepts explored in
previous chapters. You should read the first four sections sequentially; you can read
the remaining sections in any order.
Delegates
A delegate dynamically wires up a method caller to its target method. There are two
aspects to a delegate: type and instance. A delegate type defines a protocol to which
the caller and target will conform, comprising a list of parameter types and a return
type. A delegate instance is an object that refers to one (or more) target methods
conforming to that protocol.
A delegate instance literally acts as a delegate for the caller: the caller invokes the
delegate, and then the delegate calls the target method. This indirection decouples
the caller from the target method.
A delegate type declaration is preceded by the keyword delegate, but otherwise it
resembles an (abstract) method declaration. For example:
delegate int Transformer (int x);
To create a delegate instance, you can assign a method to a delegate variable:
class Test
{
static void Main()
{
Transformer t = Square; // Create delegate instance
int result = t(3); // Invoke delegate
Console.WriteLine (result); // 9
}
static int Square (int x) { return x * x; }
}
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