We have developed our back office app using web forms and Telerik reporting integrated to VS2022 (version Telerik_Reporting_2025_Q3_19_2_25_813). The application is deployed on Windows server 2022 which is not connected to Internet. Also, for security reason, the customer uses many workstations that are not connected to Internet.
With previous versions of Telerik Reporting we noticed that some Telerik's CSS files are missing because the app is trying to access them on Internet. In that case we could not open Telerik reports from PC that is not connected to Internet while it was working correctly from PC connected to Internet.
Therefore, we copied required files to a local folder (kendo.blueopal.min.css and kendo.common.min.css) and everything seemed ok.
I am not sure if the following problems appear after upgrade to the latest version but we noticed the following:
When we try to open the report from the PC which is not connected to Internet we could find following errors in the Chrome console:
DevTools failed to load source map: Could not load content for http://10.10.51.100/CEN/TCM/Content/kendo.common.min.css.map: HTTP error: status code 404, net::ERR_HTTP_RESPONSE_CODE_FAILURE
DevTools failed to load source map: Could not load content for http://10.10.51.100/CEN/TCM/Content/kendo.blueopal.min.css.map: HTTP error: status code 404, net::ERR_HTTP_RESPONSE_CODE_FAILURE
When I do the same from my PC which has Internet connection, these errors do not appear.
I have found some explanations that these errors could be ignored but the problem is that the report viewer does not display the content after these error appear.
To summarize, the same report which works correctly from my PC connected to Internet does not work from PC disconnected from internet. And both PCs are connected to the same instance of app.
On the production server, we noticed this problem when we limited IIS memory as its process used a lot of memory, and the server started running slowly. When we remove IIS memory limit, we can see errors in the console but the report shows the content correctly.
Is there a way to deploy Telerik Reporting app to not lookup to files located on Internet.
By the way, on the offline PC I see an old layout of report viewer controls and I see pages but the pages are empty:
On my PC I see different toolbar and the report shows data:
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1 Answer, 1 is accepted
Hello,
We were able to address the issue Teo encountered in a private ticket he opened, but for better visibility, I will also share our findings, as other users may come across the same problem in the future.
Problem
We have logged a bug report regarding this: ASP.NET Web Forms report viewer sends a request to https://kendo.cdn.telerik.com/themes/10.2.0/default/default-ocean-blue.css automatically. The issue was that when the report viewer page does not include a script reference for the subset for Kendo UI for jQuery components (i.e., `telerikReportViewer-kendo`), the ASP.NET Web Forms report viewer sends a request for it automatically, as well as one for the https://kendo.cdn.telerik.com/themes/10.2.0/default/default-ocean-blue.css theme from the CDN (which is not available offline).
Workaround
The workaround is to add an explicit script reference for "api/reports/resources/js/telerikReportViewer-kendo" at the top of the HTML page for the viewer, preferably within the <head> tag, and load the Kendo UI theme from a local file instead of counting on the CDN reference.
Regards,
Petar
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