I created a new WCF Application. It has a svc file & a code behind, When I try to debug (F5) then I see the following.
Open your project properties, go to the Debug tab, under start options you will see something like /client:"WcfTestClient.exe"
delete that line.
For a WCF Service Application and WCF Workflow Service Application you need to modify the .csproj.user file. A full write up can be found here.
The key part is
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