The asp.net sample assumes that the C# compiler (csc.exe) is reachable from your PATH environment variable. If you are using Visual Studio, you can make sure that it is in your path by executing the Visual Studio Command Prompt shortcut in your start menu.
From the command prompt, change your current directory to the directory containing the asp.net sample.
Build the application by executing make.bat. This batch file will invoke the Visual C# compiler to produce the output file - DotfuscatorASP.dll. This will be placed in a “bin” subdirectory of the current location. This is the default location that IIS will search for compiled code-behind assemblies.