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Editorial Team
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Asked: 2026-06-12T14:35:38+00:00

The Report Viewer Web Control HTTP Handler has not been registered in the application’s

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    The Report Viewer Web Control HTTP Handler has not been registered in the application's 
web.config file.  Add <add verb="*" path="Reserved.ReportViewerWebControl.axd" type = 
"Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=9.0.0.0, 
Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" /> to the system.web/httpHandlers section of the web.config file

This error is coming . I have already mentioned this line in http handler but still getting this error 

<add path="Reserved.ReportViewerWebControl.axd" verb="*"   type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=8.0.0.0,    Culture=neutral, PublicKeyToken=0000000000000000" validate="false" />

my html page markup is as follow 

<%@ Register Assembly="Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"
    Namespace="Microsoft.Reporting.WebForms" TagPrefix="rsweb" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<asp:Button ID="btnsubmit" runat="server" OnClick="GenerateReportButton_Click" />
    <rsweb:ReportViewer ID="ReportViewer1" runat="server">
    </rsweb:ReportViewer>
</asp:Content>

Web config assemblies section is as follows :

<assemblies>
    <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.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
    <add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
    <add assembly="System.Web.DataVisualization, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
    <add assembly="System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
    <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>
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1 Answer

  1. Editorial Team

    I was having the very same problem. What happened was I put the Report loading routine on Page_Load, and didn’t wrap it in if (!IsPostBack). The ReportViewer makes a POST to the page, and that was triggering Page_Load and reloading the report, somehow messing it up. After putting everything inside if (!IsPostBack), it worked like a charm.

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