Problem with abstract classes

[Fergal Moran]

Hello Guys

I'm a C++ programmer moving to C# and I'm trying to do something which
I regularly do in C++ and am wondering why it doesn't work in C#.

Basically in C++ I can do something similar to the following

class A{
public:
virtual void foo()=0;
};

class B : public A{
public:
virtual void foo()=0;
};

class C : public B{
public:
virtual void foo(){
cout << "Test";
}
};

Where class B and A are abstract classes with a pure virtual function
"foo"

If I try the equivalent in C#

public abstract class A {
public abstract void foo();
}
public abstract class B : A {
public abstract void foo();
}
public class C : B {
public override void foo() {
return "Hello Sailor";
}
}

I get....

error CS0533: 'B.foo()' hides inherited abstract member 'A.foo()'
error CS0534: 'C' does not implement inherited abstract member
'A.foo()'

Is this inheritance structure not valid in C# or am I missing
something.

Regards,

Fergal

[Ken Allen]

Try using the override keyword on the function definition in B.

Fergal Moran wrote:

Hello Guys

I'm a C++ programmer moving to C# and I'm trying to do something which
I regularly do in C++ and am wondering why it doesn't work in C#.

Basically in C++ I can do something similar to the following

class A{
public:
virtual void foo()=0;
};

class B : public A{
public:
virtual void foo()=0;
};

class C : public B{
public:
virtual void foo(){
cout << "Test";
}
};

Where class B and A are abstract classes with a pure virtual function
"foo"

If I try the equivalent in C#

public abstract class A {
public abstract void foo();
}
public abstract class B : A {
public abstract void foo();
}
public class C : B {
public override void foo() {
return "Hello Sailor";
}
}

I get....

error CS0533: 'B.foo()' hides inherited abstract member 'A.foo()'
error CS0534: 'C' does not implement inherited abstract member
'A.foo()'

Is this inheritance structure not valid in C# or am I missing
something.

Regards,

Fergal

[John Bailo]

public abstract class B : A
{
public *override* abstract void foo();
}
Fergal Moran wrote:

Hello Guys

I'm a C++ programmer moving to C# and I'm trying to do something which
I regularly do in C++ and am wondering why it doesn't work in C#.

Basically in C++ I can do something similar to the following

class A{
public:
virtual void foo()=0;
};

class B : public A{
public:
virtual void foo()=0;
};

class C : public B{
public:
virtual void foo(){
cout << "Test";
}
};

Where class B and A are abstract classes with a pure virtual function
"foo"

If I try the equivalent in C#

public abstract class A {
public abstract void foo();
}
public abstract class B : A {
public abstract void foo();
}
public class C : B {
public override void foo() {
return "Hello Sailor";
}
}

I get....

error CS0533: 'B.foo()' hides inherited abstract member 'A.foo()'
error CS0534: 'C' does not implement inherited abstract member
'A.foo()'

Is this inheritance structure not valid in C# or am I missing
something.

Regards,

Fergal

[Fergal Moran]

Thanks a log guys - perfect.
As also pointed out on another newsgroup - I could also have left out
the definition in class B completely.

Fergal.
Glad no-one noticed a void function returning a string :)