Question

I read a zillion articles on Auto Properties and can’t come up with a reason for NOT doing something like the following example. Am I missing something here; i.e. is there any reason I should use regular properties in this example? I do it regularly and it works fine.

In a different thread here on StackOverflow ( C#3.0 Automatic properties with extra logic ) the answer was declared to be No as in “No, automatically implemented properties have no declared implementation. Any extended implementation that you wish to provide would have to use a regular property.”

    class Foobar
{
    public string Description { get; set; }
    public bool Scary { get; private set; }

    public void Describe(int size)
    {
        if (size <= 3)
        {
            switch (size)
            {
                case 1:
                    Description = "Cute";
                    Scary = false;
                    break;
                case 2:
                    Description = "Interesting";
                    Scary = false;
                    break;
                case 3:
                    Description = "Interesting";
                    Scary = false;
                    break;
            }                
        }
        else if (size > 4 && size < 10)
        {
            Description = "I'm sweating!";
            Scary = true;
        }
        else
        {
            Description = "I'm outta here - every man for himself";
            Scary = true;
        }
    }
}

Answer 1

You’re not adding code to the get/set methods for your properties, you’re adding an entirely separate method to the class which uses the get/set properties.

If someone uses the set methods for Description or Scary directly, rather than using Describe, no custom logic is executed. As an example, nothing prevents someone from doing: obj.Describe(10); obj.Description = "Cute";. If you overloaded the set method for those properties you could prevent someone from creating such a cute and scary object.

The answer in the question that you’ve linked to is perfectly correct; you cannot add validation to the get/set methods of an auto-implemented property; if you want to you need to explicitly define the get/set methods.