Question

If I set a Friend-level scope on a setter, like this…

Public Class MyClass     Public Property IsDirty() As Boolean         Get             Return _isDirty         End Get         Friend Set(ByVal trueFalse As Boolean)             _isDirty = trueFalse         End Set     End  Property End Class 

…And then call it from another project, it works correctly. I can’t do something like MyClass.IsDirty = True.

Great! That’s exactly what I want.

But now if I define an interface, and I will indeed have to do that:

Public Interface IMyClass     Property IsDirty() As Boolean End Interface 

I can do something like:

Dim MyInstance as IMyClass= GetSomeInstanceOfMyClass() MyInstance.IsDirty=True 

…And, bizarrely, it runs! No exceptions are thrown, and the inner variable is set to True. It ignores the Friend scope completely!

That’s hideous. What am I missing??

Note: I need this because I’m designing an API, and I want the inner API to be able to set IsDirty, but end-developers shouldn’t be able to get into that. Currently I am wrapping the whole class in a facade to get this functionality, but the facade should be unecessary.

Answer 1

Interface methods always have public accessibility. You can’t fix that by explicit interface implementation, that will only hide the class method. Simply casting the object to the interface type gives unfettered access again.

EDIT: actually, the problem is easy to solve. Just declare the property ReadOnly in the interface declaration 🙂

For example:

Public Interface IMyClass     ReadOnly Property IsDirty() As Boolean End Interface  Public Class Test     Implements IMyClass     Private mIsDirty As Boolean     Private ReadOnly Property IsDirtyImpl() As Boolean Implements IMyClass.IsDirty         Get             Return mIsDirty         End Get     End Property     Public Property IsDirty() As Boolean         Get             Return mIsDirty         End Get         Friend Set(ByVal value As Boolean)             mIsDirty = value         End Set     End Property End Class