To be considered by Maya, a .NET plug-in assembly must have the extension .nll.dll; for example, myplugin.nll.dll. These DLLs must appear in the Maya plug-in path, which is defined by the Maya environment variable (MAYA_PLUG_IN_PATH). By default, this value is <…>\bin\plug-ins. Load .NET plug-ins like any other type of plug-in, via the Plug-in Manager (select Window > Settings/Preferences > Plug-in Manager) or via script.
To allow Maya to discover your compiled plug-in, you can do either of the following:
Add your plug-in assembly directory to the MAYA_PLUG_IN_PATH environment variable.