How many times did you need a property to be read-only for the users of your API, but also you needed that property to be populated by your own data access layer?
It happened to me many times, and I usually solved that problem accessing directly the underlying field changing its visibility from private to internal or protected.
But what if you want to access everything as a property and don't want to hook directly to the field?
You need to be able to specify for the setter a different visibility for the getter.
Here is how:
private int _id;
public int Id
{
get { return _id; }
internal set { _id = value; }
}
That's a feature of C# I like a lot, and that allows a lot of flexibility.
Just have to remember that the setter visibility modifier must be more restricted than the general one.
UPDATE: This feature is available only with .NET 2.0 (Thank Bill for pointing it out)