C# 5.0 Programmer's Reference

Generics and Extension Methods ❘ 353
Example program Switcher uses the following code to define a generic Switch method.
public static class Switcher
{
// Switch two values.
public static void Switch(ref T value1, ref T value2)
{
T temp = value1;
value1 = value2;
value2 = temp;
}
}
The Switch method takes a generic type T. It also takes two parameters of type T. It creates a
temporary variable of type T and uses it to swap the two values.
The following code shows how the main program uses the Switch method.
string value1 = value1TextBox.Text;
string value2 = value2TextBox.Text;
Switcher.Switch(ref value1, ref value2);
value1TextBox.Text = value1;
value2TextBox.Text = value2;
This code gets two string values from TextBoxes. It uses the Switch method to swap their values
and displays the results.
Type Not Required
In this example, Visual Studio is smart enough to infer the type parameter because
the program is passing two string values into the method. In cases such as this, the
code can omit the type parameter as in the following code.
Switcher.Switch(ref value1, ref value2);
You may want to include the type parameter anyway to make the code more
self-documenting.
Note that the Switcher class is not generic but it contains a generic method. You can also create
generic classes that contain both generic and nongeneric methods.
Generics and Extension Methods
Extension methods let you add new features to existing classes, whether they’re generic or nongeneric.
For example, suppose you have an application that uses a List. This class is a generic collection
class defined in the System.Collections.Generic namespace. It’s not defined in your code
so you can’t modify it. However, you can add extension methods to it.
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