By design .NET embeds rich Meta data inside the executable code using MSIL. Anyone can easily decompile your DLL back using tools like ILDASM (owned by Microsoft) or Reflector for.NET which is a third party. Secondly there are many third party tools which make this decompiling process a click away. So any one can easily look in to your assemblies and reverse engineer them back in to actual source code and understand some real good logic which can make it easy to crack your application. The process by which you can stop this reverse engineering is using “obfuscation”. It’s a technique which will foil the de compilers. There are many third parties (XenoCode, Demeanor for .NET) which provide .NET obfuscation solution. Microsoft includes one that is Dotfuscator Community Edition with Visual Studio.NET
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