Cast/Convert IEnumerable to IEnumerable?

Answer 1

You can't cast because they are different types. You have two choices:

1) Change the class so that PersonWithAge inherits from person.

class PersonWithAge : Person
{
        public int Age { get; set; }
}

2) Create new objects:

IEnumerable<Person> p = pwa.Select(p => new Person { Id = p.Id, Name = p.Name });

Answer 2

Use Select instead of Cast in order to indicate how to perform the conversion from one type to another:

IEnumerable<Person> p = pwa.Select(x => new Person { Id = x.Id, Name = x.Name });

Also as PersonWithAge will always contain the same properties as Person plus a couple more it would be better to have it inherit from Person.

Answer 3

You can't just cast two unrelated type into each other. You could make it possible to convert PersonWithAge to Person by letting PersonWithAge inherit from Person. Since PersonWithAge is obviously a special case of a Person, this makes plenty of sense:

class Person
{
        public int Id { get; set; }
        public string Name { get; set; }
}

class PersonWithAge : Person
{
        // Id and Name are inherited from Person

        public int Age { get; set; }
}

Now if you have an IEnumerable<PersonWithAge> named personsWithAge, then personsWithAge.Cast<Person>() will work.

In VS 2010 you will even be able to skip the cast altogether and do (IEnumerable<Person>)personsWithAge, since IEnumerable<T> is covariant in .NET 4.

Answer 4

you might want to modify your code to be something like:

class Person
{
        public int Id { get; set; }
        public string Name { get; set; }
}

class PersonWithAge : Person
{
        public int Age { get; set; }
}

Answer 5

You can keep the IEnumerable<PersonWithAge> and don't convert it to IEnumerable<Person>. Just add an implicit conversion to convert an object of PersonWithAge to Person when you need.

class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public static implicit operator Person(PersonWithAge p)
    {
        return new Person() { Id = p.Id, Name = p.Name };
    }
}

---

List<PersonWithAge> pwa = new List<PersonWithAge>
Person p = pwa[0];

Answer 6

Make PersonWithAge inherit from Person.

Like this:

class PersonWithAge : Person
{
        public int Age { get; set; }
}