I just moved my dev environment over to a Vista box, and the system.web.ext dll is version 3.5.0.0, yet my app was written on a box where the dll was a 1.6 or somthing. So in my web.config I changed all these to reference the new dll, i updated all teh projects to reference the new system.web.ext and reference the ajax toolkit dll as well. However when I run the app when i get to a page that uses those ajax controls from the toolkit i get an error:
Parser Error Message: Unable to create type 'cc1:TextBoxWatermarkExtender'. Could not load file or assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.

Problem being I don't have that assembly loaded on this machine bc its 3.5.0.0 , secondly i am not running a .net 3.5 app, its a 2.0 and I am working in VS 2005. So what do I do to fix this problem?

 Looks like your app is written in .NET 2.0, so you need the version of asp.net ajax extension for Framework 2.0 You can download it here

http://www.asp.net/ajax/downloads/

Put it in the bin folder and you should be good. Your other option is to try upgrade to 3.5

Hi Apotterosa,

Please compare your web.config with mine.  Below the sample web.config on .NET Framework 3.5.

<configuration>
	<configSections>
		<sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
			<sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
				<section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
				<sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
					<section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="Everywhere"/>
					<section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
					<section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
					<section name="roleService" type="System.Web.Configuration.ScriptingRoleServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/></sectionGroup></sectionGroup></sectionGroup></configSections><connectionStrings>
		<add name="NORTHWNDConnectionString" connectionString="Data Source=(local);Initial Catalog=NORTHWND;Integrated Security=True" providerName="System.Data.SqlClient"/>
		<add name="SIMPLELISTSConnectionString" connectionString="Data Source=(local);Initial Catalog=SIMPLELISTS;Integrated Security=True" providerName="System.Data.SqlClient"/>
	</connectionStrings>
	<system.web>
		<authentication mode="Forms"></authentication>
		<pages theme="Simple">
			<controls>
				<add namespace="AjaxControlToolkit" assembly="AjaxControlToolkit" tagPrefix="ajaxToolkit"/>
				<add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
				<add tagPrefix="asp" namespace="System.Web.UI.WebControls" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/></controls>
		</pages>
		<!--
          Set compilation debug="true" to insert debugging
          symbols into the compiled page. Because this
          affects performance, set this value to true only
          during development.
    -->
		<compilation debug="true">
			<assemblies>
				<add assembly="System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
				<add assembly="System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
				<add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
				<add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
				<add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
				<add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
				<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
				<add assembly="System.Web.Extensions.Design, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/></assemblies>
		</compilation>
		<httpHandlers>
			<remove verb="*" path="*.asmx"/>
			<add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
			<add verb="*" path="*_AppService.axd" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
			<add verb="GET,HEAD" path="ScriptResource.axd" validate="false" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/></httpHandlers>
		<httpModules>
			<add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/></httpModules></system.web>
	<system.webServer>
		<validation validateIntegratedModeConfiguration="false"/>
		<modules>
			<remove name="ScriptModule"/>
			<add name="ScriptModule" preCondition="managedHandler" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/></modules>
		<handlers>
			<remove name="WebServiceHandlerFactory-Integrated"/>
			<remove name="ScriptHandlerFactory"/>
			<remove name="ScriptHandlerFactoryAppServices"/>
			<remove name="ScriptResource"/>
			<add name="ScriptHandlerFactory" verb="*" path="*.asmx" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
			<add name="ScriptHandlerFactoryAppServices" verb="*" path="*_AppService.axd" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
			<add name="ScriptResource" verb="GET,HEAD" path="ScriptResource.axd" preCondition="integratedMode" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/></handlers></system.webServer>
	<system.web.extensions>
		<scripting>
			<webServices>
				<jsonSerialization maxJsonLength="500">
				</jsonSerialization>
			</webServices>
		</scripting>
	</system.web.extensions>
	<system.codedom>
		<compilers>
			<compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CSharp.CSharpCodeProvider,System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" warningLevel="4">
				<providerOption name="CompilerVersion" value="v3.5"/>
				<providerOption name="WarnAsError" value="false"/></compiler>
			<compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.VisualBasic.VBCodeProvider, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" warningLevel="4">
				<providerOption name="CompilerVersion" value="v3.5"/>
				<providerOption name="OptionInfer" value="true"/>
				<providerOption name="WarnAsError" value="false"/></compiler></compilers></system.codedom>
	<runtime>
		<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
			<dependentAssembly>
				<assemblyIdentity name="System.Web.Extensions" publicKeyToken="31bf3856ad364e35"/>
				<bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0"/></dependentAssembly>
			<dependentAssembly>
				<assemblyIdentity name="System.Web.Extensions.Design" publicKeyToken="31bf3856ad364e35"/>
				<bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0"/></dependentAssembly></assemblyBinding></runtime></configuration>

 http://www.asp.net/AJAX/Documentation/Live/ConfiguringASPNETAJAX.aspx

http://www.asp.net/learn/ajax-videos/

Best regards,

Jonathan

apott,

You probably already understand this, but just in case -- if you are updating everything for 3.5 (it sounds like you are) then you need to change your target framework for the project to 3.5 also, and then finally download the 3.5 version of the toolkit.

You can also just run everything as is, but then you'll need to download the 1.0.6 version of ASP.NET AJAX and install that in your GAC.  Scroll to the bottom of this page to find AJAX Extensions 1.0 for .NET 2.0.

James