If you are trying to deploy a class library project from Visual Studio to AX server and facing this error : Error 1 Unable to hot-swap the revised assembly to the server. If this is a test or development installation, configure the server to enable hot-swapping. 0 0 ITStaging it means you must enable the hot-swapping of assemblies in the AOS Configuration Form.
To do that access the AOS Server machine and open the Microsoft AX 2012 Server Configuration Form
Go to Application Object Server Tab and check “Enable the hot-swapping of assemblies for each development session” property. Take care because this operation will restart the AOS service.
After that you will be able the deploy your Visual studio project