Ajax Conflicts Between .net 2.0 and 3.5

This post is for anyone who is encountering the following errors in their asp.net applications:

• The server tag 'asp:ScriptManager' is ambiguous. Please modify the associated registration that is causing ambiguity and pick a new tag prefix.
• The base class includes the field 'ScriptManager1', but its type (System.Web.UI.ScriptManager) is not compatible with the type of control (System.Web.UI.ScriptManager).

There are many instances where you might exprience this problem. For me, the situation was that we had a virtual directory running asp.net 2.0 with AJAX extensions, while the root site is running asp.net 3.5. The subdirectory was attempting to reference the old 1.0.61025.0 version of the Web.Extensions assembly. Since we upgraded our webserver to asp.net 3.5, this assembly should no longer be used.

So the solution was to upgrade all the Web.Extensions stuff in web.config from the 1.0 to the asp.net 3.5 version. First, upgrade the configSections from this:

<configuration>    
    <configSections>        
        <sectionGroup name="system.web.extensions"
            type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral,         PublicKeyToken=31bf3856ad364e35">            
            <sectionGroup name="scripting"
 type="System.Web.Configuration.ScriptingSectionGroup, 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"/>                
                <sectionGroup name="webServices"
 type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=1.0.61025.0,             Culture=neutral, PublicKeyToken=31bf3856ad364e35">                    
                    <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="profileService"
 type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=1.0.61025.0,               Culture=neutral, PublicKeyToken=31bf3856ad364e35"
 requirePermission="false"
 allowDefinition="MachineToApplication" />
                    <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>
        </sectionGroup>
    </configSections>
</configuration>

to this:

<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>

Next, in system.web update the controls, compilation, httpHandlers, and httpModules references:

<system.web>    
    <pages>        
        <controls>            
            <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>        
        </controls>    
    </pages>    
    <compilation>        
        <assemblies>            
            <add assembly="System.Web.Extensions, 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=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>        
        <add verb="*" path="*_AppService.axd" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>        
        <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>        
        <add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>    
    </httpModules>
</system.web>

to the new 3.5 versions

<pages>    
    <controls>        
        <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>
<assemblies>    
    <add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
</assemblies>
<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>

Finally, there may be some scattered tag registrations on your pages that are still directly referencing the old version. Add a bindingRedirect to your web.config so that these references are updated to point to the correct assembly. You can add this section before or after (but not inside!) system.web

<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>

And that should do it! Our virtual directory now has no conflicts, and completely references the new asp.net 3.5 assemblies. I hope that this post was helpful, and if I left anything out, please let me know in the comments!