Since Visual Studio does not support solutions in solutions (I believe that this is a function that should be supported), the closest approximation you can create is to create groups of your projects with several solutions, so you like
- Client.sln
- Server.sln
- Master.sln who has all the projects
This adds some extra effort when changes to the solution level are made, such as adding / removing projects, but I have used this methodology previously with good success.
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