Menu: Tools -> Options -> Projects and Solutions -> General
If you don't like seeing the solution file in Solution Explorer, you can easily hide it (or show it if you have it hidden). First, let's review what the default looks like with the solution file showing:
Now if we go to Tools -> Options -> Projects and Solutions -> General and uncheck "Always show solution":
This is the result:
SPECIAL NOTE: This only works when there is one project in the solution. If you have multiple projects in your solution it will ignore this setting and give you the default view.