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Tuples
Framework 4.0 provides a new set of generic classes for holding a set of differently
typed elements. These are called tuples:
public class Tuple
public class Tuple
public class Tuple
public class Tuple
public class Tuple
public class Tuple
public class Tuple
public class Tuple
Each has read-only properties called Item1, Item2, and so on (one for each type
parameter).
You can instantiate a tuple either via its constructor:
var t = new Tuple (123, "Hello");
or via the static helper method Tuple.Create:
Tuple t = Tuple.Create (123, "Hello");
The latter leverages generic type inference. You can combine this with implicit
typing:
var t = Tuple.Create (123, "Hello");
You can then access the properties as follows (notice that each is statically typed):
Console.WriteLine (t.Item1 * 2); // 246
Console.WriteLine (t.Item2.ToUpper()); // HELLO
Tuples are convenient in returning more than one value from a method—or creating
collections of value pairs (we’ll cover collections in the following chapter).
An alternative to tuples is to use an object array. However, you then lose static type
safety, incur the cost of boxing/unboxing for value types, and require clumsy casts
that cannot be validated by the compiler:
object[] items = { 123, "Hello" };
Console.WriteLine ( ((int) items[0]) * 2 ); // 246
Console.WriteLine ( ((string) items[1]).ToUpper() ); // HELLO
Comparing Tuples
Tuples are classes (and therefore reference types). In keeping with this, comparing
two distinct instances with the equality operator returns false. However, the
Equals method is overridden to compare each individual element instead:
var t1 = Tuple.Create (123, "Hello");
var t2 = Tuple.Create (123, "Hello");
Console.WriteLine (t1 == t2); // False
Console.WriteLine (t1.Equals (t2)); // True
244 | Chapter 6: Framework Fundamentals