Description
This event allows to add additional module imports that can later be used in your events code.
Example
using System.Security.Cryptography;
Modules already included
using System;
using System.Diagnostics;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Dynamic;
using System.ComponentModel.Composition;
using System.Web;
In regards to adding third-party DLL files, check this article.