extending classes that must be used in an interface
I have created an interface as shown below. The DTO object is a complex value object with 3 parameters.

    public interface IOperation
    {
        DTO Operate(DTO ArchiveAndPurgeDTO);
    }

I need people that impliment this interface to be able to inherit from the original Value object and extend it where required.

My assumption was that they could simply inherit the DTO object, add (for example) another property and use it in the same class that impliments this interface.

When I try to use the extended value object, Visual Studio complains that I am no longer implimenting the interface.

How can I impliment this functionality.

Thanks in advance for any ideas, and/or suggestions.

Gineer
extending classes that must be used in an interface
===

I have created an interface as shown below. The DTO object is a complex value object with 3 parameters.

    public interface IOperation
    {
        DTO Operate(DTO ArchiveAndPurgeDTO);
    }

I need people that impliment this interface to be able to inherit from the original Value object and extend it where required.

My assumption was that they could simply inherit the DTO object, add (for example) another property and use it in the same class that impliments this interface.

When I try to use the extended value object, Visual Studio complains that I am no longer implimenting the interface.

How can I impliment this functionality.

Thanks in advance for any ideas, and/or suggestions.

Gineer