Method for event OnAfterUnlock

I want to promote an Item state when user unlock it.

I create a simple LifeCycle: "New"-->"Released"

I habe write this method on the server event "OnAfterUnlock":

Innovator inn=this.getInnovator();

string itemnumber = this.getProperty("item_number");
string state=this.getProperty("state","");

if ( state != "Released" ){
CCO.Utilities.WriteDebug("IP_ScadDocsPromote","Item = "+itemnumber +" State = " + state);

return this;

But it doesn't work. The log IP_ScadDocsPromote show me that the variables "itemnumber" and "state" are blank.

Thanks for your help.