Best practices: throwing exceptions from properties

Question

When is it appropriate to throw an exception from within a property getter or setter? When is it not appropriate? Why? Links to external documents on the subject would be he

Answer 1

This is all documented in MSDN (as linked to in other answers) but here is a general rule of thumb...

In the setter, if your property should be validated above and beyond type. For example, a property called PhoneNumber should probably have regex validation and should throw an error if the format is not valid.

For getters, possibly when the value is null, but most likely that is something you will want to handle on the calling code (per the design guidelines).

Answer 2

I had this code where I was unsure of which exception to throw.

public Person
{
    public string Name { get; set; }
    public boolean HasPets { get; set; }
}

public void Foo(Person person)
{
    if (person.Name == null) {
        throw new Exception("Name of person is null.");
        // I was unsure of which exception to throw here.
    }

    Console.WriteLine("Name is: " + person.Name);
}

I prevented the model from having the property being null in the first place by forcing it as an argument in the constructor.

public Person
{
    public Person(string name)
    {
        if (name == null) {
            throw new ArgumentNullException(nameof(name));
        }
        Name = name;
    }

    public string Name { get; private set; }
    public boolean HasPets { get; set; }
}

public void Foo(Person person)
{
    Console.WriteLine("Name is: " + person.Name);
}