SharePoint 2010 Windows Form App Error: The Web application at could not be found.

While trying to create a new instance of SPSite in a windows form App,we usually get an error saying "System.IO.FileNotFoundException: “The Web application at http://serverurl could not be found. Verify that you have typed the URL correctly. If the URL should be serving existing content, the system administrator may need to add a new request URL mapping to the intended application."
And usually we keep verifying again and again if we have typed URL correctly or not.
Solution for  this problem is 

 Under Project Properties –> Application, Ensure that the target framework to be compiled against is .NET Framework 3.5
 Under Project Properties –> Build, Ensure that the platform target is set to x64.
Hope it helps people in trouble....:-)