How to create a SOAP interface from the .NET DLL?

[Philipina]

Hello,

Bonjour,
I'm newbie in .NET (I usually program in Java ).
I have received the source code of a .NET DLL (framework 2.0) and I need to migrate the functionality of this DLL into a serveur application written in Java.
To do this I will modify the DLL (written in .NET) to forward all function calls into SOAP requests to my Java Soap application.
The only problem is that this DLL interface is quiet huge and if I can generate a WSDL file from the DLL definition this will help me to save a lot of time.
Then, I'm wondering if there is any possibility to generate a WSDL file from the DLL source code I have.
I don't know if you understand what I mean, this is not so easy to explain... Here below you will find a picture which should help you to understand my problem.
In blue you will see the existing part and in red you will see the part I have to develop.

Thanks in advance for your helps.

Remi.