How to solve ReportViewer error message: "An error has occurred during report processing. Input string was not in a correct format"

Article Number: 150 | Rating: 5/5 from 1 votes | Last Updated: Wed, Sep 24, 2025 at 12:13 AM

When running ReportViewer on Windows Server 2008, you may face this error message: "An error has occurred during report processing. Input string was not in a correct format". Oddly, the same ReportViewer is working fine on your local PC. So, what would be the possible cause of this issue?

The possible cause of this issue is when a ReportViewer control is dragged onto a page in your Visual Studio tool, the following code is written to the httpHandlers subsection under the system.web section of the projects Web.Config file in the projects root directory.

<system.web>

</httpHandlers>

</system.web>

When the project is deployed on IIS7, the above is not recognized and the reportviewer will not render data properly. IIS7 requires you to include that in the handlers subsection in the system.webServer section of the projects Web.Config file in the projects root directory.

To resolve the issue, the following lines need to be added to that section

<system.webServer>

<add name="Reserved-ReportViewerWebControl-axd" path="Reserved.ReportViewerWebControl.axd"

verb="*" type="Microsoft.Reporting.WebForms.HttpHandler" resourceType="Unspecified"

</handlers>

</system.webServer>

Hope this helps