If you never want the property to be editable in EPiServer or even show up there you can do;
[Ignore]
public string PropertyOnModelThatIdontWantToBeEditable { get; set; }
If you just want to update your page/blocktype to whats defined in code then you can do a "Revert to default" on the type in admin.
I think Jens' suggestion works, but keep in mind that an [Ignore] attribute will also exlude the property from indexing.
I have done some property hide using ScaffoldColumn in code. But when in Admin mode i have checked "display in edit view" check box under content type then this porperty is displayed in editor screen once again.
So how i will disable that check box "display in edit view" and hiding the property from code base permanently.So in admin no one can checked the "display in edit view" anymore.