AjaxFileUpload UploadComplete not firing

Hello,

It is my first use of AjaxFileUpload which i am trying to achieve multiple file upload (like Sharepoint Multiple File Uploader)

I installed Ajax Toolkit (Version July 2013, the latest one i assume) and i configured web config properly.

When i try to save files into server, i am getting following error. More than that, it doesnt matter what line of code i place under UploadComplete, it is not firing at all.

Any support appreceated.

ASPX

<%@ Page Title="" Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %><%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %><asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server"></asp:Content><asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server"><ajaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server"></ajaxToolkit:ToolkitScriptManager><ajaxToolkit:AjaxFileUpload ID="AjaxFileUpload1" runat="server" MaximumNumberOfFiles="10" /></asp:Content>

VB

Imports System.IO

Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub AjaxFileUpload1_UploadComplete(sender As Object, e As AjaxControlToolkit.AjaxFileUploadEventArgs) Handles AjaxFileUpload1.UploadComplete

        AjaxFileUpload1.SaveAs(Server.MapPath("~/Files/") + e.FileName)

    End Sub

End Class

This is the result