For NetSim v8 (8.0, 8.3) and v9 (9.0, 9.1) MS Visual Studio 2010 is recommended. 


For NetSim v10 and v11 (11.0, 11.1), MS Visual Studio 2015/2017 is recommended.


For NetSim v12 (12.0, 12.1),  MS Visual Studio 2017/2019 is recommended.


Visual Studio Community edition and free and can be used for editing protocol source codes in NetSim as long as “C++ Cross-Platform Library Development” module is present.


Related Knowledgebase Articles:

What components of Visual Studio Community 2017 to install and configure to work with NetSim source codes?

What components of Visual Studio Community 2019 to install and configure to work with NetSim source codes?

What is the development environment settings for NetSim v10/v11/v12?