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Why are there so many $IF DEFINED(CLR) in the VCL/RTL?
I know Delphi 7 Was Written in Object Pascal(Delphi) but since Delphi 8, released December 2003, was a .NET-only release that compiled Delphi Object Pascal code into .NET CIL; the IDE was rewritten for this purpose.
The IDE contains .Net code because the IDE is, at least in part, a .Net application. That’s completely independent of the binaries that the compiler produces from your source code.
Although the Delphi IDE helps you develop Delphi applications, that doesn’t mean the development tools all need to be written in that language. Portions are written in C++, C#, and assembler, too.