The Web application at http://contoso.com 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.

This is the message you can receive, when you try to run your application(winform or console) on SharePoint Application.
The reason is that a application runs on x86.
Here are a few steps which will help you (I hope):
1.Right-Click on the application -> Properties:

2. Build -> Platform target :

3. Change it on "Any CPU" and "Save":