Operation canceled when I define an attribute StateAction

Hi,

When I define the function following in the VaultApplication class, M-Files cancel the state action.
In debug, I don't reach the line of code.
Do you have a sample code to use the attributes please.

    [StateAction("XONYX_QM_ST_APPLICABLE")]
    public void WorkflowStateAction(StateEnvironment env) {
      xQMT.finalDocUpdateVersion(env.Vault, env.ObjVer);
    }

Thanks