C# 4 and .NET 4

s u m m a r y ❘ 149
The Tuple < > class offers two Equals() methods: one that is overridden from the Object base class
with an object as parameter, and the second that is defi ned by the IStructuralEqualityComparer
interface with object and IEqualityComparer as parameters. Another tuple can be passed to the fi rst
method as shown. This method uses EqualityComparer < object > .Default to get an ObjectEqualityCom
parer < object > for the comparison. This way every item of the tuple is compared by invoking the Object.
Equals() method. If every item returns true , the fi nal result of the Equals() method is true , which is
the case here with the same int and string values:
if (t1.Equals(t2))
Console.WriteLine("the same content");
You can also create a custom IEqualityComparer , as shown with the class TupleComparer . This class
implements the two methods Equals() and GetHashCode() of the IEqualityComparer interface:
class TupleComparer: IEqualityComparer
{
public new bool Equals(object x, object y)
{
return x.Equals(y);
}
}
public int GetHashCode(object obj)
{
return obj.GetHashCode();
}
code snippet StructuralComparison/Program.cs
The implementation of the Equals() method of the IEqualityComparer interface
requires the new modifi er or an implicit interface implementation because the base
class Object defi nes a static Equals() method with two parameters as well.
The TupleComparer is used, passing a new instance to the Equals() method of the Tuple < T1, T2 > class.
The Equals() method of the Tuple class invokes the Equals() method of the TupleComparer for every
item to be compared. So with the Tuple < T1, T2 > class, the TupleComparer is invoked two times to check
whether all items are equal:
if (t1.Equals(t2, new TupleComparer()))
Console.WriteLine("equals using TupleComparer");
summary
In this chapter, you ’ ve seen the C# notation to create and use simple, multidimensional, and jagged arrays.
The Array class is used behind the scenes of C# arrays, and this way you can invoke properties and methods
of this class with array variables.
You ’ ve seen how to sort elements in the array by using the IComparable and IComparer interfaces. You ’ ve
learned using and creating enumerators, the interfaces IEnumerable and IEnumerator , and the yield
statement. You ’ ve seen tuples, a new feature of .NET 4.
Moving on, the next chapter focuses on operators and casts.
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