How to get ZipFiles to work (C#) (Error CS0246: The type or namespace 'ZipFile' could not be found (are you missing a using directive or an assembly reference?))

I’m trying to get this script to extract a .zip file into a folder.

Here’s the code I have:

string zipToUnpack = "New folder.zip";
        string unpackDirectory = "files2";
        using (ZipFile zip1 = ZipFile.Read(zipToUnpack))
        {
            // here, we extract every entry, but we could extract conditionally
            // based on entry name, size, date, checkbox status, etc.  
            foreach (ZipEntry e in zip1)
            {
                e.Extract(unpackDirectory, ExtractExistingFileAction.OverwriteSilently);
            }
        }

My using references are:

using System;
using System.Windows.Forms;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Net;
using System.IO.Compression;

When I try to compile this, I get this error:
code.cs(120,16): error CS0246: The type or namespace name ‘ZipFile’ could not be
found (are you missing a using directive or an assembly reference?)
code.cs(120,31): error CS0103: The name ‘ZipFile’ does not exist in the current
context

If I have to add a reference or something, PLEASE show me how with code because I don’t know how and I don’t like to use Visual Studio to add references.

Just try to put it into “Plugins” Folder, if you don’t have then just create it in assets folder, and then Sync it by(Assets->Sync Monodevelop Project")…