如何解决这个ajaxToolkit错误？

Question

For reference, this is what I want to create: http://imgur.com/IBEiyJv

Error 1 Unknown server tag 'ajaxToolkit:CalendarExtender'.

<ajaxToolkit:CalendarExtender FirstDayOfWeek="Monday" PopupPosition="BottomLeft"
                TargetControlID="FirstTrafficDate" OnClientDateSelectionChanged="ValidateDate"
                ID="calDate" Format="yyyy-MM-dd" PopupButtonID="CalBtn1" runat="server" />

This is code I copied from another part of my webpage from which it works fine, but on this new page it gives me this error. I've made sure that AjaxToolkit updates properly (thanks to people helping me earlier) but now I am not sure what the problem is. Any ideas?

Answer 1

This error may apperar if you forgot to add this section in web.config:

<system.web>
  <pages>
    <controls>
      <add namespace="AjaxControlToolkit" assembly="AjaxControlToolkit" tagPrefix="ajaxToolkit"/>
    </controls>
  </pages>
</system.web>

Alternatively, you may want to add <%@ Register tag in your page's aspx code instead of modifying web.config:

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit"
    TagPrefix="ajaxToolkit" %>