Synchronizing a ListDictionary

  • Thread starter Thread starter Allen Jones
  • Start date Start date
A

Allen Jones

Hi,

I tried to extend ListDictionary in order to create a thread safe version
named SynchronizedListDictionary.

Despite the docs saying the properties and methods of ListDictionary are
virtual, when I try to compile my derived class, the compiler tells me that
I "cannot override inherited member XXX because it is not marked virtual,
abstract, or override".

I know there are other collections and techniques that I can use as an
alternative, but I want to understand how a method can be listed as virtual
in the docs (which I thought came straight from the source) but the compiler
doesnt recognize it as such.

Thanks

Regards
Allen
 
Try using "new". It doesn't override the virtual method, but it will be
called when referenced in the context of your customized class.

Jon
 
Hi Jon,

Thanks for the input, but as I said in my post, I am not after work arounds
or alternatives. I want to understand why this does not work the way it
should.

Regards
Allen
 
Hi,

I tried to extend ListDictionary in order to create a thread safe version
named SynchronizedListDictionary.

Despite the docs saying the properties and methods of ListDictionary are
virtual, when I try to compile my derived class, the compiler tells me that
I "cannot override inherited member XXX because it is not marked virtual,
abstract, or override".

I know there are other collections and techniques that I can use as an
alternative, but I want to understand how a method can be listed as virtual
in the docs (which I thought came straight from the source) but the compiler
doesnt recognize it as such.

Thanks

Regards
Allen
Click to expand...

How did you override it? Using VS2003, this works:
public class MyDict:ListDictionary,IDictionary
{
public MyDict()
{
}
private class myDict:IDictionary
}


When you type myDict:IDictionary, VS will show a little tip that says:
"Press TAB to implement stubs for interface
System.Collections.IDictionary"

Does that work for you?
 
Austin,

Its the individual members that cause a problem when I compile them. e.g.

public class SynchronizedListDictionary : ListDictionary {

// other stuff

public override void Add(object key, object value) {
// method implementation
}
}

In the example the Add method causes the compiler to report the message:
Add(object, object) canot override
System.Collections.Specialized.ListDictionary.Add(object,object) because it
is not marked virtual, abstract, or override.

The problem is, according to the docs, ListDictionary.Add IS virtual.

Regards
Allen
 
Yes, I have tried it & I agree there seems to be a discrepancy between the
docs and real life.

I appreciate you are not looking for workarounds, but just for information,
you can override the interface explicitly i.e.:

void IDictionary.Add(object key, object value);

However, this may not be ideal in all circumstances.

S.
 
Well. looking at the rotor source code, it does appear that the
documentation is wrong. It's declared as:

public void Add(object key, object value)
{
//stuff
}

So, it's another error in the documentation.
 
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