Sometimes I get the following error while I was doing HttpWebRequest to a WebService. I copied my code below too.
System.Net.WebException: Unable to connect
I got this error in an application that uses AppFabric. The clue was getting a DataCacheException in the stack trace. To see if this is the issue for you, run the following PowerShell command:
@("AppFabricCachingService","RemoteRegistry") | % { get-service $_ }
If either of these two services are stopped, then you will get this error.