The Report Viewer Web Control HTTP Handler has not been registered in the application's web.config file

For IIS 7 or later


<system.webServer>
<handlers>
<add name="ReportViewerWebControlHandler" preCondition="integratedMode" verb="*" path="Reserved.ReportViewerWebControl.axd" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91" />
</handlers>
</system.webServer>

I don't have enough rep to comment on the existing answers, but the reason why may need to change your app pool from Integrated to Classic is because of [this MSDN entry][1]

With an Integrated app pool you only need the handlers part, with a Classic app pool you need both handlers and httpHandlers.


[1]:

[To see links please register here]

The same issue for me. The issue also went away for me
1)when I changed the app pool from Integrated to Classic.
2) change HTTP handler like this


<httpHandlers>
<add verb="*" path="Reserved.ReportViewerWebControl.axd" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91" validate="false" />
</httpHandlers>

In my case, It was resolved by adding the below lines just next to <system.web> in the web.config


<system.webServer>
<handlers>
<add name="ReportViewerWebControlHandler" preCondition="integratedMode" verb="*" path="Reserved.ReportViewerWebControl.axd" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=15.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91" />
</handlers>
</system.webServer>

The issue was I was using IIS 7 or above on my server. The issue got resolved as I added this section to my code.





<system.webServer>
<validation validateIntegratedModeConfiguration="false"/>
<modules runAllManagedModulesForAllRequests="true"/>
<handlers>
<add name="ReportViewerWebControlHandler" preCondition="integratedMode" verb="*" path="Reserved.ReportViewerWebControl.axd" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=15.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91" />
</handlers>
</system.webServer>