The question is poorly formulated, so no one can be 100% sure what path do you mean.
For a currently running application, you can find a path to the main module of its entry assembly, which is usually some *.EXE file:
string exeFile =
System.Reflection.Assembly.GetEntryAssembly().Location;
Note: there are several other methods, but some of them are not reliable (not universal enough) as the result depends on how the application is hosted; for example, it might give different result when hosted as a Windows Service application by a Service Controller or even by Visual Studio debug host.
—SA