When you are using VSCode with Unity you may get an error like:
OmniSharp
The reference assemblies for framework ".NETFramework,Version=v4.5" were not found.
- Install .net SDK 4.5.2 - http://www.microsoft.com/en-au/download/details.aspx?id=42637
- Go to your .net references folder -
C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework
- Make a copy of the folder 4.5.2
- Rename your copy of 4.5.2 to 4.5
- Restart VSCode