Csharp (C#) is a language developed by Microsoft for running applications in .NET platforms (.NET Framework and .NET).
The .NET Framework generator (formally so-called since GeneXus 17 Upgrade 8) enables the generation of Web applications in C# for the .NET Framework (4.x). The programs generated are C# code sources (.cs) and compiled into assemblies (.dll or .exe) in a common intermediate language (IL), which, in runtime, are interpreted by the .NET virtual machine.
The applications communicate with the database through ADO.NET, and possible DBMS to be used are all those supported by GeneXus: DB2 UDB for iSeries, DB2 Universal Database, Informix, MySQL, Oracle, PostgreSQL, and SQL Server.
Check the corresponding requirements listed in the following article GeneXus 18 hardware and software requirements.
The generator will be maintained following Microsoft's strategy related to the .NET Framework.
New features in GeneXus may be available only in the .NET Generator.
So, new projects should use the GeneXus .NET Generator instead, and others moved to .NET when possible because evolution will happen in that generator, according to Microsoft's strategy of .NET.
For further information read the following article: Comparing the .NET generator with the .NET Framework generator.