static void Main()
{
// Allowed in C# 4.0
Pair <Contact> contacts =
new Pair <Contact>(
new Contact("Princess Buttercup"),
new Contact("Inigo Montoya"));
IReadOnlyPair <PdaItem> pair = contacts;
PdaItem pdaItem1 = pair.First;
PdaItem pdaItem2 = pair.Second;
}
public void CovariantTest()
{
Pair <EmailContact> contacts = new Pair <EmailContact> {
First = new EmailContact {
Id = 1, EmailAddress = "*****@*****.**"
},
Second = new EmailContact {
Id = 2, EmailAddress = "*****@*****.**"
}
};
// This assignment would fail if not for the covariant (out T) type parameter.
// By default, IReadOnlyPair<Email> and Pair<EmailContact> are not convertable.
IReadOnlyPair <ContactMethod> baseContacts = contacts;
Assert.Equal(1, baseContacts.First.Id);
Assert.Equal(2, baseContacts.Second.Id);
}
