Visual Studio not showing all Projects in solution

Open your ".sln" project file using Notepad. In this file you can observe listed projects like below

Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "test.myProject.Data", "test.myProject.Data\test.myProject.csproj", "{6D7F7B84-F3BD-4A19-A069-D144C345B887}"

Please add if there any missing projects. If you have old back up or co-workers file, Just copy and paste missing projects to this file. In my case it works !!

close vs , delete .vs folder then open vs again. it works for me.

I found that re-adding the existing project to the solution worked for me!