hi there; first off, don't let the amount of web.config code below scare you off ... there is only a small portion (that i've indicated) which doesn't work.  i posted it all just for reference purposes. 

anyway, i have 2 sites ... an autoComplete and a cascadingDropDown.

each site only have 1 control and each site works fine.

however, when i try to add the autoComplete to the cascadingDropDown site, i receive a 'sys is undefined' error.

i've done a lot of research and this seems to be a common problem ... often solved by adding:

<add verb="GET" path="ScriptResource.axd" type="Microsoft.Web.Handlers.ScriptResourceHandler" validate="false"/>

to the  <httpHandlers>  tag.

this did not work for me.

in comparing my 2 web.config files, i found some inconsistancies in the <httpHandlers> tag.  i will post my entire web.config first:

<configuration>

<sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">

<section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="MachineToApplication"/>

<section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="Everywhere" />

<section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" allowDefinition="MachineToApplication" />

</sectionGroup>

<sectionGroup name="microsoft.web" type="Microsoft.Web.Configuration.MicrosoftWebSectionGroup">

<section name="webServices" type="Microsoft.Web.Configuration.WebServicesSection" requirePermission="false"/>

<section name="profileService" type="Microsoft.Web.Configuration.ProfileServiceSection" requirePermission="false"/>

<microsoft.web>

<add type="Microsoft.Web.Script.Serialization.Converters.DataSetConverter"/>

<add type="Microsoft.Web.Script.Serialization.Converters.DataTableConverter"/>

<webServices enableBrowserAccess="true"/>

<add name="myConnectionString" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\myDB.mdf;Integrated Security=True;User Instance=True" providerName="System.Data.SqlClient" />

<system.web>

<controls>

<add namespace="Microsoft.Web.UI" assembly="Microsoft.Web.Atlas" tagPrefix="atlas"/>

<add namespace="AjaxControlToolkit" assembly="AjaxControlToolkit" tagPrefix="ajaxToolkit"/>

</controls>

<buildProviders>

</buildProviders>

<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>

<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

<add assembly="System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

<httpHandlers>

<add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" validate="false"/>

</httpHandlers>

<httpModules>

</httpModules>

<validation validateIntegratedModeConfiguration="false"/>

<add name="ScriptModule" preCondition="integratedMode" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>

<handlers>

<add name="ScriptHandlerFactoryAppServices" verb="*" path="*_AppService.axd" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>

</handlers>

</configuration>

okay, that is my web.config.

as i mentioned, i've isolated the <httpHandlers> tag as the issue.

if i leave it as it is, neither the autoComplete or the cascadingDropDown controls work.

however, if i comment out the following <add> tag from the  <httpHandlers> section, :

then the cascadingDropDown control works fine (while the autoComplete is still dead).

now, if i UN-comment out the above <add> tag (so that it is active), and comment out this <add> tag instead:

then the autoComplete control works fine (but the cascadingDropDown dies).

so, apparently, the issue is, it appears that i can have one AJAX control or the other ... but not both. 

when they're all un-commented out, there's something that's cancelling the other out.

is there someone out there who knows how to resolve this?

a big thanks! in advance!

Hi chubbs,

Based on your description,  I think your two web sites are developed based on different Asp.Net Ajax versions.  "Microsoft.Web.Services.ScriptHandlerFactory"  is the evidence.So my suggestion is you should do this step by step:

1.   Udate your Asp.Net Ajax Extension to the latest version.

2.  Create  an Ajax-Enabled Web site and copy it's web.config to your project.

3. Modify on the new web.config file if need.

Hope this helps. If there's something wrong , please post here.