.NET Reactor is a powerful code protection and software licensing system for software written for the .NET Framework, and supports all languages that generate .NET assemblies.

When you compile a program written for the Microsoft .NET framework, the program you provide to your users is not compiled into a native executable program, but instead is translated into something called the Common Intermediate Language instructions (CIL). CIL is half way between source code and native code, and is interpreted by the .NET framework when your program is run, rather than executed directly as machine code. Because of this, the source code of your application or library can be easily reproduced. Tools such as .NET Reflector can reproduce source code from a compiled .NET assemblies in seconds, and in the .NET language of your choice! Clearly, commercial software distributed to end users without some form of protection is wide open to piracy and intellectual property theft.

The traditional solution to intellectual property protection in .NET is to use 'obfuscation', indeed Microsoft make an obfuscation utility available to Visual Studio users.

Its' main features are

Intellectual property protection
-NecroBit Protection
-Native Code generation
-Code Virtualization
-Obfuscation
-Control Flow Obfuscation
-Hide Method Calls (dynamic proxy)
-String Encryption
-Anti Tampering
-Anti Debugging
-Resource Encryption and Compression
-Dependency Merging
-Protects full applications and libraries (dlls)

Powerful licensing system
-Create trial versions of your software
-Set an expiration date
-Limit use to a fixed number of days after installation
-Limit by number of uses
-Limit to use for no more than a set number of minutes each invocation
-Limit trial version functionality
-Easily turn your trial version into a fully licensed version
-License your software
-Permanently (non expiring license)
-By time period (i.e rent your software)
-By number of uses (i.e software as a service)

Software development kit
-Integrate license checking into you assembly and extend licensing fuctionality
-Extend licensing functions with bespoke extensions.

Deployment
-Create .NET Core single file application bundles

System Requirements
-IBM compatible PC with Pentium class microprocessor.
-Windows 2000/2003/XP with 512 MB RAM, Windows 2008/Vista/7/8/8.1/10/11 with 1 GB RAM.
-Administrative access is required to install to Windows NT/2000/XP/Vista or Windows 7/8/8.1/10.
-.NET Framework 4.0 or higher.