Yes, you can use Visual Studio to create and edit CORE HL7 C# Scripts! Watch the YouTube video below which gives you step-by-step instructions on how to use Microsoft Visual Studio (even the free editions) to create your CORE HL7 C# Scripts.
Edit CORE HL7 Scripts in Visual Studio
While you cannot actually compile and run your CORE HL7 C# scripts in Visual Studio, the Sandbox dll only contains "stub" properties, methods, and classes to let Visual Studio give you the "Intellisense" help while you are writing your code, you CAN use the Visual Studio editor to create your code which you can then copy and paste into your CORE HL7 Script Library.
As shown in the video above you will need the CORE HL7 Script Sandbox DLL.