CHAPTER 9 COLLECTIONS AND GENERICS
}
b = temp;
No doubt, you can see where this is going. If you also needed to swap floating-point numbers,
bitmaps, cars, buttons, and whatnot, you would have to build even more methods, which would become
a maintenance nightmare. You could build a single (nongeneric) method that operated on object
parameters, but then you face all the issues you examined earlier in this chapter, including boxing,
unboxing, a lack of type safety, explicit casting, and so on.
Whenever you have a group of overloaded methods that differ only by incoming arguments, this is
your clue that generics could make your life easier. Consider the following generic Swap method that
can swap any two Ts:
// This method will swap any two items.
// as specified by the type parameter .
static void Swap(ref T a, ref T b)
{
Console.WriteLine("You sent the Swap() method a {0}",
typeof(T));
T temp;
temp = a;
a = b;
b = temp;
}
Notice how a generic method is defined by specifying the type parameters after the method name,
but before the parameter list. Here, you state that the Swap() method can operate on any two
parameters of type . To spice things up a bit, you also print out the type name of the supplied
placeholder to the console using C#’s typeof() operator. Now consider the following Main() method,
which swaps integers and strings:
static void Main(string[] args)
{
Console.WriteLine("***** Fun with Custom Generic Methods *****\n");
// Swap 2 ints.
int a = 10, b = 90;
Console.WriteLine("Before swap: {0}, {1}", a, b);
Swap(ref a, ref b);
Console.WriteLine("After swap: {0}, {1}", a, b);
Console.WriteLine();
// Swap 2 strings.
string s1 = "Hello", s2 = "There";
Console.WriteLine("Before swap: {0} {1}!", s1, s2);
Swap(ref s1, ref s2);
Console.WriteLine("After swap: {0} {1}!", s1, s2);
}
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Console.ReadLine();