How can I reuse custom renderer to another Xamarin Form's project?

I have write a custom render to Solution A.
project A, item: BaseEntry.cs
project A.Droid : BaseEntryRenderer.cs
project A.iOS: BaseEntryRenderer.cs

If I want to reuse the baseEntry to Solution B.
I don't want to copy the code to Project B, project B.Droid, project B.iOS.
How can I do ?

So I want to write dll library for this issue.
I can create the project type: Class Library (Xamarin.Forms). and Create BaseEntry.cs in it. But How can I do for android native project / iOS native project?