Could not load file or assembly 'Microsoft.ReportViewer.WebForms'


I am trying to use the report viewer in and have uploaded my site. However, when my page containing the report viewer is loaded, it shows the following error:

Could not load file or assembly 'Microsoft.ReportViewer.WebForms, Version=, Culture=neutral, PublicKeyToken=89845dcd8080cc91' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

This is my first time deploying an ASP.NET website, so I'm not sure what the problem is.
asked on Stack Overflow May 11, 2013 by Krishna • edited May 22, 2015 by KyleMit

13 Answers


This link gave me a clue that I didn't install a required update (my problemed concerned version nr, v11.0.0.0)

ReportViewer 2012 Update 'Gotcha' to be aware of

I installed the update SQLServer2008R2SP2

I downloaded ReportViewer.msi, which required to have installed Microsoft® System CLR Types for Microsoft® SQL Server® 2012 (look halfway down the page for installer)

In the GAC was now available WebForms v11.0.0.0 (C:\Windows\assembly\Microsoft.ReportViewer.WebForms v11.0.0.0 as well as Microsoft.ReportViewer.Common v11.0.0.0)

answered on Stack Overflow Sep 5, 2013 by EricG • edited Feb 17, 2020 by Madis Otenurm

I've installed Microsoft.ReportViewer.2012.Runtime nuget package and problem has been solved without installing ReportViewer.msi or sql feature pack 12

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answered on Stack Overflow Oct 8, 2015 by Kasper Roma • edited May 16, 2018 by Moses Machua

You need to reference both Microsoft.ReportViewer.WebForms and Microsoft.ReportViewer.Common and set the CopyLocal property to true. This will result in the dll's being copied to our bin directory (both are necessary).

answered on Stack Overflow Sep 12, 2013 by jmoreno

I've solved the problem by copying both

  • Microsoft.ReportViewer.WebForms.dll from C:\Program Files (x86)\Microsoft Visual Studio 12.0\ReportViewer
  • and Microsoft.reportviewer.common.dll from C:\Program Files\Microsoft Office\Office15\ADDINS\PowerPivot Excel Add-in

into bin folder (website).

Of course web.config must have:

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


        <add assembly="Microsoft.ReportViewer.WebForms, Version=, Culture=neutral, PublicKeyToken=89845DCD8080CC91" />
        <add assembly="Microsoft.ReportViewer.Common, Version=, Culture=neutral, PublicKeyToken=89845DCD8080CC91" />

        <add extension=".rdlc" type="Microsoft.Reporting.RdlBuildProvider, Microsoft.ReportViewer.WebForms, Version=, Culture=neutral, PublicKeyToken=89845dcd8080cc91" />

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

And that's all. For me is ok.

Hope this helps.

answered on Stack Overflow Apr 11, 2015 by CDSwSrl • edited Apr 11, 2015 by blackbishop

I ran into the same error. My web app was pointed towards report viewer version 10.0 however if 11.0 is installed it adds a redirect in the 10.0 .dll to 11.0. This became an issue when 11.0 was uninstalled as this does not correct the redirect in the 10.0 .dll. The fix in my case was to simply uninstall and reinstall 10.0.

answered on Stack Overflow May 20, 2014 by user3657646

I had this error with an old webforms app. Turns out there was a line in the markup causing the issue. I removed it and the error disappeared.

<%@ Register assembly="Microsoft.ReportViewer.WebForms, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" namespace="Microsoft.Reporting.WebForms" tagprefix="rsweb" %>
answered on Stack Overflow Feb 22, 2016 by Steve Greene

I had this error when going from version, i.e. "Microsoft.ReportViewer.WebForms, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />

to version, i.e.

"Microsoft.ReportViewer.WebForms, Version=, Culture=neutral, PublicKeyToken=89845dcd8080cc91"

It took a while until I understood that not only the version was changed but also the public token key, as you can see above.

answered on Stack Overflow Oct 20, 2016 by GunnarS

I had the same error for a different package. My problem was that a dependent project was referencing a different version. I changed them to be the same version and all was good.

answered on Stack Overflow Jun 3, 2017 by Taran

My solution is:

  1. Copy dll Microsoft.ReportViewer.WebForms.dll into Bin folder in your project.
  2. Remove your reference.
  3. Add new reference from bin folder.

I hope this can help.

answered on Stack Overflow Dec 12, 2017 by Hamlet Mendez

Updating ReportViewer should works. Use below instruction to install updated ReportViewer from Nuget Package Manager console.

Install-Package Microsoft.ReportingServices.ReportViewerControl.WebForms

Just add below assembly reference in your aspx file.

Here, is the version number of the ReportViewerControl.WebForms that was installed in my VS. Please check Reference of the Solution to confirm the version number. No need to add PublicTokens (if multiple installation exists, it may creates trouble again).

answered on Stack Overflow Mar 17, 2019 by mirzapinku

Upload the file Microsoft.ReportViewer.WebForms.dll to your bin directory of your web applicaion.

You can find this dll file in the bin directory of your local web application.

answered on Stack Overflow May 11, 2013 by Amit Mittal

My trial version of DevExpress had expired. Try renewing it again.


In order to Run Report Viewer On server with Data from Server

A) Go to Project Property ----> Select Reference ------> Add Reference

1) Import (Microsoft.ReportViewer.Common.dll)-----> (Path "C:\Program Files (x86)\Microsoft Visual Studio 10.0\ReportViewer")

2) Import (Microsoft.ReportViewer.ProcessingObjectModel.dll) -----> (Path "C:\Windows\Assembly\GAC_MSIL\Microsoft.ReportViewer.ProcessingObjectModel")

3) Import (Microsoft.ReportViewer.WebForms.dll)-----> (Path "C:\Program Files (x86)\Microsoft Visual Studio 10.0\ReportViewer")

B) In Above three DLL set its "Local Copy" to True so that while Building Deployment Package it will getcopied to "Bin" folder.

C) Publish the Solution

D) After that Upload all the files along with "Bin" folder with the help of "File Zilla" software to "Web Server".

E) This will install DLL on server hence, client is not required to have "Report Viewer.dll".

This worked for me.

answered on Stack Overflow Jun 13, 2019 by Hemal Shah • edited Jun 13, 2019 by Hemal Shah

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