I\'m running my Web Project in IIS.
It is a 4.0 Framework APP.
I have a Service.svc and I get this error when I run my Application.
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I got this error after I accidentally published one website into the directory of another website. The two websites had different versions of .net. What fixed it for me was changing the application pool. To do that, in the IIS manager:
click the website => Advanced Settings... (on the right) => click to the right of Application Pool => a button with "..." should appear => select ".NET v4.5 Classic"
If that application pool doesn't work, try some of the others.