I was recently working on a reporting web application that uses the Report Viewer ( ReportViewer ) control that ships with SQL Server Reporting Services (SSRS). The Report Viewer control was rendering perfectly when I was developing using Visual Studio 2008. The trouble started when I published the web application to an IIS 7.0 server. The Toolbar was completely broken and showed up something like this.

SSRStoolbar

<rsweb:ReportViewer AsyncRendering="false" ID="reportViewer" Width="100%" Height="100%" runat="server" SizeToReportContent="True" > </rsweb:ReportViewer>

Initially it looked like just the images where missing. But the toolbar was completely broken. The toolbar of the Report Viewer control relies on images and JavaScript that are generated dynamically. It uses a call to the Reserved.ReportViewerWebControl.axd to dynamically generate the images and the JavaScript. Something like

GET /Reserved.ReportViewerWebControl.axd?OpType=Resource&Version=9.0.30729.1&Name=Microsoft.Reporting.WebForms.Icons.NextPage.gif HTTP/1.1

GET /Reserved.ReportViewerWebControl.axd?OpType=Resource&Version=9.0.30729.1&Name=Microsoft.Reporting.WebForms.Icons.LastPage.gif HTTP/1.1

When you use the Report Viewer Control Visual Studio edits your web.config to map a Http Handler to respond to these requests.

<system.web>
  <httpHandlers>
  <add path="Reserved.ReportViewerWebControl.axd" verb="*" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" validate="false"/>
  </httpHandlers>
</system.web>

The above entry tells ASP.NET that whenever a call is made to ReportViewerWebControl.axd use the Microsoft.Reporting.WebForms.HttpHandler assembly to execute it.

This mapping is very important because if you remove it the web server will return a 404 “File Not Found” error code because the ReportViewerWebControl.axd does not exist physically on the server.

Strangely when I checked the IIS 7.0 logs for the broken scenario I found that all requests for ReportViewerWebControl.axd had failed with a 404.

With IIS 7.0 there was an architectural change. There were changes to the web.config structure as well. The <httpHandlers> section that was under the <system.web> has now moved to <handlers> under <system.webServer>

Visual Studio had edited the web.config based on the IIS 6.0 model and had made an entry for the Http Handler under the <httpHandler> section. With IIS 7.0 this section is no longer read. So we need to make the proper entries for the Http Handler that handles the calls to ReportViewerWebControl.axd

<system.webServer>
    <handlers>
    <add name="ReportViewerWebControl" path="Reserved.ReportViewerWebControl.axd" verb="*" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
    </handlers>
</system.webServer>

IIS 7.0 will now understand that whenever a call is made to ReportViewerWebControl.axd it needs to route it to the Http Handler Microsoft.Reporting.WebForms.HttpHandler

Cross posted from Vijay’s Blog ( http://blogs.msdn.com/vijaysk/archive/2009/01/14/report-viewer-toolbar-does-not-render-properly-on-iis-7-0.aspx )