Why is it impossible to override a getter-only property and add a setter? [closed]

Answer 1

I agree that not being able to override a getter in a derived type is an anti-pattern. Read-Only specifies lack of implementation, not a contract of a pure functional (implied by the top vote answer).

I suspect Microsoft had this limitation either because the same misconception was promoted, or perhaps because of simplifying grammar; though, now that scope can be applied to get or set individually, perhaps we can hope override can be too.

The misconception indicated by the top vote answer, that a read-only property should somehow be more "pure" than a read/write property is ridiculous. Simply look at many common read only properties in the framework; the value is not a constant / purely functional; for example, DateTime.Now is read-only, but anything but a pure functional value. An attempt to 'cache' a value of a read only property assuming it will return the same value next time is risky.

In any case, I've used one of the following strategies to overcome this limitation; both are less than perfect, but will allow you to limp beyond this language deficiency:

   class BaseType
   {
      public virtual T LastRequest { get {...} }
   }

   class DerivedTypeStrategy1
   {
      /// get or set the value returned by the LastRequest property.
      public bool T LastRequestValue { get; set; }

      public override T LastRequest { get { return LastRequestValue; } }
   }

   class DerivedTypeStrategy2
   {
      /// set the value returned by the LastRequest property.
      public bool SetLastRequest( T value ) { this._x = value; }

      public override T LastRequest { get { return _x; } }

      private bool _x;
   }