Sometimes we need to create an empty solution and add new projects to that solution.This approach comes handy when you first just want your empty solution within a folder structure and then you later want to just add new projects to this solution.
1.One possible solution is to Enable “Always Show Solution” in the Projects And Solution Tree inside the Options in Visual Studio.If you enable this then whenever you create a new project a solution will also be created for you with that project.This sometimes is a problem when we create only a single website and want a .sln or “solution file” to load that project. 
2. Another approach is just navigate to Other Project Types and in that go the subtree “Visual Studio Solutions” and here you will find “Blank Solution” template, this will open for you a blank solution into which you can add projects. 
Initially there will be no projects loaded as we have not created any project.Just right click the solution and go to Add and then add new project,add new website, add existing project,add existing website what ever you feel like. 
Happy Programming!!!!