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Debug vs. release in .NET
Debug/Release difference
What is the difference between Release and Debug modes in Visual Studio while building a project?
Well, it depends on what language you are using, but in general they are 2 separate configurations, each with its own settings. By default, Debug includes debug information in the compiled files (allowing easy debugging) while Release usually has optimizations enabled.
As far as conditional compilation goes, they each define different symbols that can be checked in your program, but they are language-specific macros.