Can a Web Service be part of an C# Application

[GeeeTeee]

Hi. Could anyone provide help to a newbie please?

I have just started writing a C# application which transmits data to a web
service, so it is effectively a client. I have that working fine.

I now need to add code which will allow the application to behave as a web
service, accepting data from a web service client.

I hope this makes sense to you out there, and I may be asking a simple
question here, or I may be asking the impossible!

Any ideas?

Thanks.