title: Problems with using ajax toolkit in asp.net
body: <p>First I installed AjaxControlToolkit, run the "Install-Package AjaxControlToolkit" this command in the Package Manager Console. Then, I did add register AjaxControlToolkit at the top of the page and also in the web.config for the whole project. In between, I did go through some q&amp;a like <a href="https://stackoverflow.com/questions/2943537/problem-with-ajax-toolkit-asp-net-visual-basic">Ajax Toolkit ASP.NET (Visual Basic) Not Displaying Calendar</a>. Unfortunately, my project still cannot integrated with AjaxControlToolkit and I got the error as below. </p>
  
  <p>"<strong>Error    2   Unknown server tag 'ajaxToolkit:CalendarExtender'.  C:\Users\admin\Documents\Visual Studio 2010\WebSites\testing\testing.aspx   8</strong> 
  ". </p>
  
  <p>Thanks for reading and appreciate for any reply.</p>
  
  <p>This is the message that I got from Package Manager Console and the coding attached below are testing.aspx and web.config .</p>
  
  <p><strong>PM> Install-Package AjaxControlToolkit
  'AjaxControlToolkit 4.1.51116' already installed.
  testing already has a reference to 'AjaxControlToolkit 4.1.51116'.</strong></p>
  
  <p><strong>testing.aspx</strong></p>
  
  <pre><code>&lt;%@ Register TagPrefix="asp" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit"%&gt;
  &lt;%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="testing.aspx.cs" Inherits="testing" %&gt;
  
  &lt;asp:Content ID="Content1" ContentPlaceHolderID="main" Runat="Server"&gt;
      &lt;asp:ScriptManager ID="ScriptManager1" runat="server"&gt;
  &lt;/asp:ScriptManager&gt;
      &lt;asp:TextBox ID="Date1" runat="server"&gt;&lt;/asp:TextBox&gt;
      &lt;ajaxToolkit:CalendarExtender ID="CalendarExtender1" runat="server" TargetControlID="Date1"&gt;
  &lt;/ajaxToolkit:CalendarExtender&gt;
  &lt;/asp:Content&gt;
  </code></pre>
  
  <p><strong>web.config</strong></p>
  
  <pre><code>&lt;?xml version="1.0"?&gt;
  &lt;!--
    For more information on how to configure your ASP.NET application, please visit
    http://go.microsoft.com/fwlink/?LinkId=169433
    --&gt;
  &lt;configuration&gt;
    &lt;connectionStrings&gt;
      &lt;add name="ConnectionString" connectionString="Data Source=navi.thegigabit.com;Persist Security Info=True;User ID=summerap;Password=summerap1" providerName="System.Data.SqlClient"/&gt;
    &lt;/connectionStrings&gt;
    &lt;system.web&gt;
      &lt;customErrors mode="Off"/&gt;
      &lt;compilation debug="true"&gt;
        &lt;assemblies&gt;
          &lt;add assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/&gt;
          &lt;add assembly="System.Web.Extensions.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
          &lt;add assembly="System.ServiceModel.Activation, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/&gt;
          &lt;add assembly="System.Runtime.Serialization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Web.ApplicationServices, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/&gt;
          &lt;add assembly="System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/&gt;
          &lt;add assembly="System.Configuration, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/&gt;
          &lt;add assembly="System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Xml, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Web.Services, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/&gt;
          &lt;add assembly="System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Data.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/&gt;
          &lt;add assembly="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.ServiceModel.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/&gt;
          &lt;add assembly="System.Data.Services.Client, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Data.Services.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Data.Entity, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/&gt;
          &lt;add assembly="System.Web.DynamicData, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/&gt;
          &lt;add assembly="System.ComponentModel.DataAnnotations, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/&gt;
          &lt;add assembly="System.Web.Entity, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
          &lt;add assembly="System.Xml.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
        &lt;/assemblies&gt;
      &lt;/compilation&gt;
      &lt;pages&gt;
        &lt;controls&gt;
          &lt;add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
          &lt;add namespace="AjaxControlToolkit" assembly="AjaxControlToolkit" tagPrefix="asp" /&gt;
        &lt;/controls&gt;
      &lt;/pages&gt;
  
      &lt;httpHandlers&gt;
        &lt;remove verb="*" path="*.asmx" /&gt;
        &lt;add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
        &lt;add verb="*" path="*_AppService.axd" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
        &lt;add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" validate="false" /&gt;
      &lt;/httpHandlers&gt;
  
      &lt;httpModules&gt;
        &lt;add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
      &lt;/httpModules&gt;
  
    &lt;/system.web&gt;
  &lt;/configuration&gt;
  </code></pre>