Build error ubuntu
As soon as i try to build the server i get below error

`/usr/share/dotnet/sdk/3.0.100/Microsoft.Common.CurrentVersion.targets(1175,5): error MSB3644: The reference assemblies for .NETFramework,Version=v4.5 were not found. To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application. You can download .NET Framework Developer Packs at https://aka.ms/msbuild/developerpacks [/home/pool/wwwserver/server/Server/Server.csproj]`

Anyone any idea on how to solve this since framework is windows only....