C#

/// Start the service
protected override void OnStart(string[] args)
{
    ServiceDesktopPermission();
}

/// Using Management Object services the option "Allow service to interact with desktop"
/// can be enabled. This gets unchecked/disabled each time a new install or update of the
/// service is performed.
static public void ServiceDesktopPermission()
{
   try
   {
	ConnectionOptions coOptions = new ConnectionOptions();
		
	coOptions.Impersonation = ImpersonationLevel.Impersonate;
		
	// CIMV2 is a namespace that contains all of the core OS and hardware classes.
	// CIM (Common Information Model) which is an industry standard for describing 
	//        data about applications and devices so that administrators and software 
	//        management programs can control applications and devices on different 
	//        platforms in the same way, ensuring interoperability across a network. 
			    
	ManagementScope mgmtScope = new ManagementScope(@"root\CIMV2", coOptions);
		
	mgmtScope.Connect();
		
	ManagementObject wmiService;

	wmiService = new ManagementObject("Win32_Service.Name='" + "My Service Name" + "'");
		
	ManagementBaseObject InParam = wmiService.GetMethodParameters("Change");
		
	InParam["DesktopInteract"] = true;
		
	wmiService.InvokeMethod("Change", InParam, null);
      }
   catch(Exception ex)
   {
     //TODO: Log this error
   }
}