override confusing

[burbakei]

i have a class like this

Public Class A
Public Overridable Sub F()
End Sub

Public Overridable Sub F(ByVal x As Integer)
End Sub
End Class

i want to inherit a class from Class A like this

Public Class B
Inherits A

Public Overrides Sub F(ByVal x As Integer)
End Sub
End Class

but i get a compile error that says

sub 'F' cannot be declared 'Overrides' because it does not override a sub in a base class.

when i rearrange Class A and change the location of the two overloaded methods it will be ok:

Public Class A
Public Overridable Sub F(ByVal x As Integer)
End Sub

Public Overridable Sub F()
End Sub
End Class

can anybody tell me why it is so?

thankX

[hellswraith]

That is weird. It seems that the compiler is stopping at the first sub, and not looking further. I don't know if this is by design, or if it is a bug. I will look for an answer, but can't guarantee it.

[Edneeis]

It must declare the unused overridable function with Overloads and thus requires it on that one was well, because if you add Overloads then it works:

Public Class A
    Public Overridable Sub F()
    End Sub
 
    Public Overridable Sub F(ByVal x As Integer)
    End Sub
End Class
 
Public Class B
    Inherits A
 
    Public [b]Overloads[/b] Overrides Sub F(ByVal x As Integer)
    End Sub
End Class

[Cander]

you need to specify the overloads keywords for those overloaded methods

Public Class A
    Public Overridable Overloads Sub F()
    End Sub
 
    Public Overridable Overloads Sub F(ByVal x As Integer)
    End Sub
End Class
 
Public Class B
    Inherits A
 
    Public Overloads Overrides Sub F(ByVal x As Integer)
    End Sub
End Class

[Cander]

darn..too slow..:-\

[Pirate]

Darn it! Edneeis just beat me to that
this maybe clearer Edneeis's is also will work perfect.

Public Class A
        Public Overridable Overloads Sub F()
        End Sub
 
        Public Overridable Overloads Sub F(ByVal x As Integer)
        End Sub
    End Class
 
 
 
    Public Class B
        Inherits A
 
        Public Overloads Overrides Sub F(ByVal x As Integer)
 
        End Sub
    End Class

[Pirate]

Cander as well

[burbakei]

in Class A you are free to write down Overloads or omit it.
we can always use Overloads Overrides in a derived class if the signature of the method is exactly like the signature of the method in base class. now AGAIN i ask why in the second version of Class A everything is ok (even without Overloads keyword) but in the first version something is wrong?

[Cander]

bug?

[Pirate]

the problem in your Code exists in Class B since you're trying to inherit Class A which contains 2 Subs with the same Sub names without telling your compiler that you want to overload(making many versions of the same Sub name) the Sub that has the same signature.Class B ,directs the Compiler to inherits Class A.Then , excute next line which is

Public  Overrides Sub F(ByVal x As Integer)
 
End Sub

Now ,the Compiler found that you are inherting the sub called " F " ,he will go to Class A but found 2 Subs have the same names.
in this case, you have to tell your compiler to take care because there are many Subs or Functions have the same name but I want the Sub with this identical signature.So just write Overloads.

Edneeis's way is fine but if you want it more clear , add Overloads keyword to both Subs.

[burbakei]

@pirate

so why compiler does not report any error if i write the class like this:

Public Class A
Public Overridable Sub F(ByVal x As Integer)
End Sub

Public Overridable Sub F()
End Sub
End Class

it is all my question about.

[Pirate]

You do not have to use the Overloads keyword when you are defining multiple overloaded Subs in the same class. This is only required when inhertiance is applied(from another Class).

[burbakei]

@pirate

i am not asking about overloading methods in the same class. what do you mean by saying that? i am asking about a behavior of vb.net compiler about overriding an overloaded method from a base class in a derived class.

[Pirate]

in another words........????

[burbakei]

in another words i can say

there are 10 kinds of people in the world. those who understand binary and those don't understand binary.

[Pirate]

Well , if you can't pose your question in VB.NET language ,it's better you stop programming

[burbakei]

@pirate

it was already written in a plain way. if you read it carefully you didnot get a low level machine dependent message.
by the way i assume this is a free of charge site to help people promote their knowledge not to say them quit programming. sooner or later i will get the answer to my PLAIN (not a binary one) question and i will share with those who still go on programming vb.net

[Pirate]

Well , I think I expalined everything about Overriding @ Overloading methods , but you need the whole day to understand what I POSTED.If it's difficult to understand then keep away boy!

[Pirate]

Overriding & Overloading

[daidaluus]

i tested the two versions of Class A and got that strange compile time error in the first version of Class A and no error in the second one. but in the last one compiler sends a warning message saying method shadowing. i dont know if shadows is the problem or not but i work on it and sent you the result, if any.

daidaluus