System.Linq.Dynamic not found

Hello,
I am trying to use the c# 6 method:

System.Linq.Dynamic.DynamicExpression.ParseLambda()

Though i get the error:

The type or namespace name ‘Dynamic’ does not exist in the namespace ‘System.Linq’ (are you missing an assembly reference?)

My API compatibility level is set to .NET 4.x, my Platform is Windows. Scripting Backend is IL2CPP.

Edit:

Similary,

 System.Data.Entity

can’t be found…

Found a solution. One needs to manually import the assembly .dll into Assets/Plugins.