在Visual Studio和。net中编译条件文件

I am developing a software tool for my company. I am using Visual Studio, C# and targeting .NET 4.0. One of requirements is the software will be released in three versions (limited, standard and extended). There are several interns/trainee in my company as well as some regular employees and managers. And each group will be given other version of the software. The limited version for interns, the standard one for employees and the extended one for managers. Theese are requirements given to me. Moreover, it must be one executable file (no dll files) for each version.I am developing a software tool for my company.