How Can I Call a Base Class Method From a Derived Class That Has Overridden It?

Calling base.base.method() Exceptionally

When deriving classes from a base structure, the base keyword allows access to members defined in the immediate parent class. However, in exceptional situations, there may be a need to invoke methods from classes further up the inheritance hierarchy.

Consider the provided code scenario, where Derived overrides the Say() method of Base. Within SpecialDerived, a subsequent override of Say() calls base.Say(), intending to execute Say() from Base.

Expected vs. Actual Behavior

The expected output is:

Called from Special Derived.
Called from Base.

However, due to the nature of method overriding, the actual output includes an unexpected call to Say() from Derived:

Called from Special Derived.
Called from Derived.
Called from Base.

Addressing the Issue

Since direct invocation of base.base.method() is not supported, an alternative approach is necessary. The provided updated implementation in SpecialDerived demonstrates this:

class SpecialDerived : Derived
{
    public override void Say()
    {
        Console.WriteLine("Called from Special Derived.");
        CustomSay(); // Calls CustomSay() from Derived instead of Say()
        base.Say();
    }

    protected virtual void CustomSay()
    {
        Console.WriteLine("Called from Derived.");
    }
}

By defining an additional protected virtual method, CustomSay(), Derived can handle the desired behavior without affecting other derived classes.

Alternative Reflection Approach

In scenarios where modifying the inheritance structure is not feasible, a reflection-based approach can be employed as shown below:

class SpecialDerived : Derived
{
    public override void Say()
    {
        Console.WriteLine("Called from Special Derived.");
        var ptr = typeof(Base).GetMethod("Say").MethodHandle.GetFunctionPointer();            
        var baseSay = (Action)Activator.CreateInstance(typeof(Action), this, ptr);
        baseSay();            
    }
}

This approach utilizes reflection to dynamically retrieve the Say() method from Base and execute it directly, circumventing the standard method resolution process.

The above is the detailed content of How Can I Call a Base Class Method From a Derived Class That Has Overridden It?. For more information, please follow other related articles on the PHP Chinese website!