To all other other people who encountered
Error Creating Control and 'RSClientController' is undefined when attaching ReportViewer version 9.0 to VS 2012, i got the solution.
What i did is to set my web config file and asp.net source below
Report.aspx
<%@ Register assembly="Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" namespace="Microsoft.Reporting.WebForms" tagprefix="rsweb" %>
Web.Config
<httpHandlers>
<add verb="*" path="Reserved.ReportViewerWebControl.axd" type = "Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
</httpHandlers>
<compilation debug="true" targetFramework="4.0">
<assemblies>
<add assembly="Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
<add assembly="Microsoft.ReportViewer.Common, Version=9.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
</assemblies>
</compilation>
<system.webServer>
<validation validateIntegratedModeConfiguration="false"/>
<modules runAllManagedModulesForAllRequests="true"/>
<handlers>
<add name="Reserved-ReportViewerWebControl-axd" path="Reserved.ReportViewerWebControl.axd" verb="*" type="Microsoft.Reporting.WebForms.HttpHandler" resourceType="Unspecified" preCondition="integratedMode"/>
</handlers>
</system.webServer>
Even though on the Designer View, Report Viewer still show Error Creating Control but when you run your application, the report will render normally.
Hope this will help you.
Best Regards