MaestroAPI targets MGOS 2.0 (and MGEP 2010). The HttpServerConnection can work with any version of MapGuide, but the LocalNativeConnection needs the correct version of MapGuideDotNetApi.dll Unfortunately the official MapGuideDotNetApi.dll has varying version numbers, and is usually not signed. To use the LocalNativeConnction with 1.2 or 2.1, you must use a signed version of MapGuideDotNetApi.dll. The Web.Config file shows how to add a bindingRedirect for a ASP.Net application, the same can be done for a regulat executable. Just rename Web.Config to match your executable, eg MyApp.exe -> MyApp.exe.config. If you need a special version of MapGuideDotNetApi.dll, eg. for a development version of MapGuide, you can sign the dll by issuing this command: ..\signer.exe -k ..\..\maestroapi.key -outdir .\out -a MapGuideDotNetApi.dll