Accessing overrriden public property in C#

Question

This is the scenario:

class BaseClass
{
    public virtual string Prop {get; set;}
}

class ChildClass : BaseClass
{
    public override string Prop {get; set;}
}

//program
...
ChildClass instance = new ChildClass;
Console.WriteLine(instance.Prop); //accessing ChildClass.Prop
...

The question is how to access BaseClass.Prop in a instance of ChildClass? Will casting do the trick?

Console.WriteLine((instance as BaseClass).Prop); //accessing BaseClass.Prop

-EDIT- A lot of people suggested casting. In C++ it would not work because polymorphism would still ensure that the child property is called. Isn't that the case in C#?

In C++ you would solve the issue by doing:

instance.(BaseClass::get_Prop())

Answer 1

You can't do that in a simple way from the outside. Inside ChildClass you can access it through base.Prop.

Note also that casting it will not make any difference. Consider the following code:

class BaseClass
{
    string _prop = "base prop";
    public virtual string Prop
    {
        get { return _prop; }
        set { _prop = value; }
    }
}

class ChildClass : BaseClass
{
    private string _childProp = "child prop";
    public override string Prop
    {
        get { return _childProp; }
        set { _childProp = value; }
    }

    public string PropFromBase
    {
        get { return base.Prop; }
        set { base.Prop = value; }
    }
}


Console.WriteLine((new ChildClass()).Prop);  // writes "child prop"
Console.WriteLine((new ChildClass() as BaseClass).Prop);  // writes "child prop"
Console.WriteLine((new ChildClass()).PropFromBase);  // writes "base prop"

Note however that in your code example you have not overridden the property; you have hidden it, which means that you essentially created a brand new property that just happens to have the same name. In the code example that I show above it is overridden instead, using the virtual keyword in the base class and the override keyword in the child.

Answer 2

Cast the instance of ChildClass to an instance of BaseClass; i.e. use:

((BaseClass)childClassInstance).Prop

Answer 3

Don't you get a compiler error for that code?

In any case, ChildClass.Prop does not override BaseClass.Prop - it hides it. You should really declare it as

    public new string Prop {get; set;}

You can access any member from the base class via base.Member. In this case, base.Prop.

Answer 4

Just like for any base member: base.Prop

Answer 5

Console.WriteLine(((BaseClass)instance).Prop); //BaseClass.Prop

This works because the property isn't overridden, it's hidden. If you added the "override" keyword to the derived class property, it would no longer work.

Answer 6

BaseClass baseInstance = instance as BaseClass;
Console.WriteLine(baseInstance .Prop); //accessing BaseClass.Prop

Answer 7

Your ChildClass's Prop property is hiding BaseClass's Prop property. This should be a compiler warning.

EDIT: You'll have to decide which behavior you want, polymorphism or new property declaration, since c# allows for both.

• use virtual/override for polymorphic behavior
• use new for "new-but-same-name" property behavior

Answer 8

Use the new keyword along with the conversion and it should work

such as public new string Prop { [...] } and Console.WriteLine((instance as BaseClass).Prop);

Answer 9

The semantics of overriding a property won't let you access the base of an overridden property. And this makes sense. Classes that use ChildClass shouldn't care if the property is overridden or not. When the property is used by another class it's up to ChildClass to return the appropriate value.

Usually questions like these indicate an attempt to solve a different problem. What kind of problems are you facing that you need direct access to the base property?