accessing protected method in extension class

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Posted on by dark_knight

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Hello,

I wrote an extension for the standard class A, method A. Then there is class C that inherits from class B, which inherits from class A. Class C is instantiated and at some point in time C.methodA() is called. Now according to debugger i'm in ClassA.methodA. Can I call somehow protected method ClassC.methodD() from classA.methodA() extension? VS tells me there is no methodD on classA. However, in debugger when i'm in classA.methodA() "this" variable is class C.

Thanks.

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Dynamics 365 Finance

Microsoft Dynamics AX

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Martin Dráb 235,979 Most Valuable Professional on at

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accessing protected method in extension class

You can't do it without casting. If the type of variable is ClassA, the static type control doesn't allow you to call method that the class doesn't have. If you want to use methods of ClassC, you need to cast the object to ClassC.

Why do you want to avoid casting and use some other trick? Casting is exactly what you need, isn't it?

Alternatively you can add methodD() to ClassA and override it in ClassC. Then ClassA (and all its children) has methodD() and you call it on variables of type ClassA. If the ClassA variable happen to contain ClassC object, the ClassC implementation of methodD() will be called. That's polymorphism.

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dark_knight 913 on at

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accessing protected method in extension class

Sohaib, hi

please read this

https://learn.microsoft.com/en-us/dynamics365/fin-ops-core/dev-itpro/extensibility/method-wrapping-coc

protected methods can be wrapped so I don't see any problems here

also

When you wrap a method, you can also access public and protected methods, and variables of the base class.

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dark_knight 913 on at

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accessing protected method in extension class

Hi Martin,

Yes. I know about access modifier and casting. but is it possible to do without casting somehow? some trick or anything like that. because the idea was to use existing method on class C to check the context table

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Sohaib Cheema 47,936 User Group Leader on at

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accessing protected method in extension class

+ Know the basics about access providers

Public

Private

Internal

Protected

Protected Internal

these are basics of Object Oriented Programming

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Martin Dráb 235,979 Most Valuable Professional on at

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accessing protected method in extension class

The key concepts you need to learn about object-oriented programming are casting and polymorphism.

It seems that you have a variable of type ClassA, which - at runtime - contains an instance of ClassC. But the compiler doesn't know that (if) there will be ClassC instance; it works with the declared type, which is ClassA. And it doesn't have any methodD(), therefore the compiler correctly rejects such a call.

If you want to use members of ClassC, you need to cast the variable to ClassC. For example:

ClassC c = objA; c.methodD();

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André Arnaud de Cal... 297,785 Super User 2025 Season 2 on at

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accessing protected method in extension class

Hi Dark knight,

It is hard to follow your question. Are you able to mention the standard classes and methods and provide the functional business requirement?
Initially, I think you need to extend class C, but not sure.

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