Adding to what has been said, another option is have your C# DLL exposed as a REST API and then call it from your app using the new RESTClient object in PowerScript.  I personally think this is the best way to do it because it paves the way to cloud-enable your app in the future.

You want to use the .NET DLL Importer on the Tools menu, or on the File->New->Tool tab.  Note that many .Net DLLs out of the box won't support some of the limitations PowerBuilder has on the classes that it can import.  If that is the case with the .NET DLL you wish to import you'll need to create a wrapper DLL for it that accommodates the PowerBuilder restrictions.  For that you would need a C# compiler, such as SnapDevelop or Visual Studio.

Hi Francisco;

  To have the C# SNAPDev environment, you need to be using the "CloudPro" edition of Appeon PB 2019 Rx. SnapDev comes with that PB edition.

  Note that in R3, you now also have the ability to access a .Net Assembly directly as well using the new DotNetObject Object Class.

HTH

Regards ... Chris