If you have no source but know its architecture then you have a choice. If it is .NET then you can load it reflectively with powershell. Powersploit's DLLInjection module shows this though is a little different with exes as you have to find the entry point and execute it. (if it takes parameters, you have to feed it the parameters as it wants them ie string[]..even if you have no parameters but exe can take some you need to give it those object types empty).
aaliyah mendes