Use dropzone.js with asp.net

If you review the article

File upload in ASP.NET MVC using Dropzone JS and HTML5

You will see an example in aspx at the end

HTML: WebFormDropzoneDemo.aspx

Code: WebFormDropzoneDemo.aspx.cs

then use

<script src="Scripts/dropzone/dropzone.min.js"></script>

<script type="text/javascript">
    //File Upload response from the server
    Dropzone.options.dropzoneForm = {
        maxFiles: 2,
        url: "WebFormDropzoneDemo.aspx",
        init: function () { ....

defines the aspx in the url and basically the upload of the file is done in Page_Load

public partial class WebFormDropzoneDemo : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            SaveUploadedFile(Request.Files);
        }
}

is where it takes the Request.Files that sends dropzone