C# 4 and .NET 4

148 ❘ ChaPTer 6 ArrAys And tuples
}
}
this.LastName == other.LastName;
code snippet StructuralComparison/Person.cs
Now two arrays containing Person items are created. Both arrays contain the same Person object with
the variable name janet, and two different Person objects that have the same content. The comparison
operator != returns true because there are indeed two different arrays referenced from two variable
names persons1 and persons2. Because the Equals() method with one parameter is not overridden
by the Array class, the same happens as with the == operator to compare the references, and they are not
the same:
var janet = new Person { FirstName = "Janet", LastName = "Jackson" };
Person[] persons1 = {
new Person
{
FirstName = "Michael",
LastName = "Jackson"
},
janet
};
Person[] persons2 = {
new Person
{
FirstName = "Michael",
LastName = "Jackson"
},
janet
};
if (persons1 != persons2)
Console.WriteLine("not the same reference");
code snippet StructuralComparison/Program.cs
Invoking the Equals() method defined by the IStructuralEquatable that is the method with the
first parameter of type object and the second parameter of type IEqualityComparer, you can define
how the comparison should be done by passing an object that implements IEqualityComparer. A
default implementation of the IEqualityComparer is done by the EqualityComparer class. This
implementation checks if the type implements the interface IEquatable, and invokes the IEquatable.
Equals() method. If the type does not implement IEquatable, the Equals() method from the base class
Object is invoked to do the comparison.
Person implements IEquatable, where the content of the objects is compared and the arrays
indeed contain the same content:
if ((persons1 as IStructuralEquatable).Equals(persons2,
EqualityComparer.Default))
{
Console.WriteLine("the same content");
}
You’ll see next how the same thing can be done with tuples. Here, two tuple instances are created that
have the same content. Of course, because the references t1 and t2 reference two different objects,
the comparison operator != returns true:
var t1 = Tuple.Create(1, "Stephanie");
var t2 = Tuple.Create(1, "Stephanie");
if (t1 != t2)
Console.WriteLine("not the same reference to the tuple");
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