Question

I have a base class “Parent” like this:

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication1
{
    class Parent
    {
        private int parentVirtualInt = -1;
        public virtual int VirtualProperty
        {
            get
            {
                return parentVirtualInt;
            }
            set
            {
                if(parentVirtualInt != value)
                {
                    parentVirtualInt = value;
                }
            }
        }
    }
}

and a child class like this:

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication1
{
    class Child : Parent
    {
        public override int VirtualProperty
        {
            get
            {
                if(base.VirtualProperty > 0)
                {
                    throw new ApplicationException("Dummy Ex");
                }
                return base.VirtualProperty;
            }
            set
            {
                if(base.VirtualProperty != value)
                {
                    base.VirtualProperty = value;
                }
            }
        }
    }
}

Note that the getter in Child is calling the getter of Parent (or at least this is what I intend).

I now use the “Child” class by instantiating it, assigning a value (let’s say 4) to its VirtualProperty and then reading the property again.

Child c = new Child();
c.VirtualProperty = 4;
Console.Out.WriteLine("Child.VirtualProperty: " + c.VirtualProperty);

When I run this, I obviously get an ApplicationException saying “Dummy Ex”. But if I set a breakpoint on the line

if(base.VirtualProperty > 0)

in Child and check the value of base.VirtualProperty (by hovering the mouse over it) before the exception can be thrown (I assume(d)), I already get the Exception. From this I convey that the statement base.VirtualProperty in the “Child-Getter calls itself”; kind of.

What I would like to achieve is the same behavior I get when I change the definition of parentVirutalInt (in Parent) to protected and use base.parentVirtualInt in the Getter of Child instead of base.VirtualProperty. And I don’t yet see why this is not working. Can anybody shed some light on this? I feel that overridden properties behave differently than overridden methods?

By the way: I am doing something very similar with subclassing a class I do not have any control over (this is the main reason why my “workaround” is not an option).

Kind regards

Answer 1

It is (arguably) a bug in the debugger. You can add your vote to this feedback article. This isn’t easy to fix, I’m sure, the debugger doesn’t have ready access to the base property getter method address since the v-table slot for the property getter has been replaced in the derived class.

One possible workaround is to store the base value in a local variable first so you can inspect that one. That isn’t going to make your getter any slower.