title: AJAX - TagPrefix is not registered
body: <p>I have looked at code on <a href="https://stackoverflow.com/questions/20297043/unknown-server-tag-ajaxtoolkithtmleditorextender">Unknown server tag &quot;ajaxToolkit:HtmlEditorExtender&quot;</a> but am still stuck so would appreciate a second pair of eyes.</p>
  
  <p>What I want to do is then, on submit, pass the HTML code to a string and save it. (I am only trying to get the HTML Editor to work at this point!) </p>
  
  <p>Error: HTML EditorExtender. -- This control cannot be display because its TagPrefix is not registered in this Web Form</p>
  
  <p>'######</p>
  
  <p>I have tried adding </p>
  
  <pre><code>&lt;pages&gt;
                &lt;controls&gt;
                    &lt;add tagPrefix="ajaxToolkit" assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" /&gt;
                &lt;/controls&gt;
            &lt;/pages&gt;
  </code></pre>
  
  <p>But then pages comes up as invalid as well. </p>
  
  <p>Newbie on AJAX. </p>
  
  <p>I have </p>
  
  <p>AjaxControlToolkit.dll in the bin folder as well as ajaxcontroltoolkit.pdb</p>
  
  <p>Whole code below:</p>
  
  <p>Default.aspx</p>
  
  <pre><code>&lt;%@ Page Title="Default" Language="VB"  AutoEventWireup="false"  CodeFile="Default.aspx.vb" Inherits="_Default" %&gt;
  
  &lt;%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %&gt;
  
  &lt;%@ Register  
      Assembly="AjaxControlToolkit"  
      Namespace="AjaxControlToolkit.HTMLEditor"  
      TagPrefix="HTMLEditor" %&gt;  
  
       &lt;%@ Register
  Assembly="AjaxControlToolkit"
  Namespace="AjaxControlToolkit.HTMLEditor"
  TagPrefix="HTMLEditor" %&gt;
  
  &lt;asp:TextBox runat="server"
          ID="txtBox1" 
          TextMode="MultiLine" 
          Columns="50" 
          Rows="10" 
          Text="Hello &lt;b&gt;world!&lt;/b&gt;" /&gt;
  
  
   &lt;ajaxToolkit:HtmlEditorExtender ID="replyBody_HtmlEditorExtender" runat="server" Enabled="True" OnImageUploadComplete="saveFile"  ClientIDMode="AutoID" EnableSanitization="true"  TargetControlID="replyBody"&gt;
  
      &lt;p&gt;Test page shows&lt;/p&gt;
  </code></pre>
  
  <p>Default.aspx.vb</p>
  
  <pre><code>Partial Class _Default
      Inherits System.Web.UI.Page
  
  End Class
  </code></pre>
  
  <p>Web.Config</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="ApplicationServices" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\aspnetdb.mdf;User Instance=true" providerName="System.Data.SqlClient"/&gt;
    &lt;/connectionStrings&gt;
    &lt;system.web&gt;
        &lt;compilation debug="true" strict="false" explicit="true" targetFramework="4.0"&gt;
  
  
            &lt;pages&gt;
                &lt;controls&gt;
                    &lt;add tagPrefix="ajaxToolkit" assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" /&gt;
                &lt;/controls&gt;
            &lt;/pages&gt;
  
  
            &lt;assemblies&gt;
          &lt;add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/&gt;
          &lt;add assembly="System.Web.Extensions.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/&gt;
          &lt;add assembly="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/&gt;
        &lt;/assemblies&gt;
      &lt;/compilation&gt;
      &lt;authentication mode="Forms"&gt;
        &lt;forms loginUrl="~/Account/Login.aspx" timeout="2880"/&gt;
      &lt;/authentication&gt;
      &lt;membership&gt;
        &lt;providers&gt;
          &lt;clear/&gt;
          &lt;add name="AspNetSqlMembershipProvider" type="System.Web.Security.SqlMembershipProvider" connectionStringName="ApplicationServices" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="false" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10" applicationName="/"/&gt;
        &lt;/providers&gt;
      &lt;/membership&gt;
      &lt;profile&gt;
        &lt;providers&gt;
          &lt;clear/&gt;
          &lt;add name="AspNetSqlProfileProvider" type="System.Web.Profile.SqlProfileProvider" connectionStringName="ApplicationServices" applicationName="/"/&gt;
        &lt;/providers&gt;
      &lt;/profile&gt;
      &lt;roleManager enabled="false"&gt;
        &lt;providers&gt;
          &lt;clear/&gt;
          &lt;add name="AspNetSqlRoleProvider" type="System.Web.Security.SqlRoleProvider" connectionStringName="ApplicationServices" applicationName="/"/&gt;
          &lt;add name="AspNetWindowsTokenRoleProvider" type="System.Web.Security.WindowsTokenRoleProvider" applicationName="/"/&gt;
        &lt;/providers&gt;
      &lt;/roleManager&gt;
    &lt;/system.web&gt;
    &lt;system.webServer&gt;
      &lt;modules runAllManagedModulesForAllRequests="true"/&gt;
    &lt;/system.webServer&gt;
  
  &lt;/configuration&gt;
  </code></pre>