I was moving some code around and had a nice WCF Service Interface and Service Class created. So I copied them into a new project where I was re-creating my work.

When I tried to debug (self-host) the service, just to test it out with the embedded WCF Test Client.

But I kept getting this error:

"The client was unable to retrieve service metadata. Make sure the service is running and exposing metadata."

This made no sense. My config file was fine. I even created a new WCF service in the solution, confirmed that it worked properly, then compared the config files line by line.

No problems.

After going around in circles for a while (including getting zero google results for that error message), a thought occurred to me. I copied and pasted the entire contents of the Interface and the service class. I hadn't changed the namespace!

That was the problem. I fixed the namespace and the service ran in the Test Client just fine.