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HTML5 Viewer Troubleshooting

The article provides troubleshooting for commonly met issues with the HTML5 Viewer and its MVC and WebForms wrappers.

The recommended troubleshooting approach for the HTML5 Viewer is to use Fiddler or other proxy tool to check the requests, their responses and statuses. With Fiddler, information about requests and responses content can be seen in Fiddler - Inspectors - Request/Response - Raw tabs. This will let you check requests to the Reporting REST service and determine if its URLs are correct and the relative paths are resolved correctly. Relative paths may need adjustment depending on how the application is hosted - ASP.NET Web Project Paths.

Another option to troubleshoot web applications is to use Fiddler Jam. It installs as a browser extension and collects logs for requests and responses performed in the browser. The logs are securely stored and later can be shared with a third party for examination through a simple URL. Fiddler Jam is being actively developed and might be a better choice than Fiddler in terms of deployment and integration.

The HTML5 Viewer displays content rendered through the Reporting HTML Rendering mechanism.

Error loading the report viewer's templates. (Template = /api/reports/resources/templates/telerikReportViewerTemplate-html).

The error message indicates that the Reporting REST service is not responding. Check the HTML5 Viewer's serviceUrl and adjust the relative path. Test adding "~" or remove the first "/" - ASP.NET Web Project Paths. It is recommended to test the service by address in browser - step 8 of How To: Add Telerik Reporting REST Web API to Web Application. The issue might be related to WebAPI controllers duplicating routes, which can be avoided by changing the registered by default Telerik Reporting REST Web API routes.

Report Parameters are not updated on refreshing the HTML5 Viewer

The HTML5 Viewer sends information about the client's reportSource.parameters in a JSON-formatted string. Test updating JSON.NET NuGet package to the latest official version through the Visual Studio NuGet Package Manager Dialog. Also verify that the HTML5 Viewer's persisSession is set to false.

Error Client with ID 'xxxxxx-xxxx' not found. Expired.

The error message indicates that the viewer's ID cannot be found in the cache storage. Such error can occur if the time set as Reporting REST service's ClientSessionTimeout has expired - Cache Management, or if the Reporting REST service's Storage is not set accordingly the hosting enviroment - REST Service Storage.

Access to the path 'xxxxxx\value.dat' is denied.

The error message indicates that the Reporting REST service cannot access the configured file storage. Verify the Reporting REST service has an unique HostAppId in its configuration and the application has read/write access to the folder specified by the FileStorage instance in the Reporting REST service configuration - REST Service Storage.

The HTML5 Report Viewer does not display a report that uses Table/List/Crosstab item in Internet Explorer.

In case data visualized by the Table/List/Crosstab item results in a great number of HTML elements, Internet Explorer may fail to visualize the content. solutions are suggested in Design Considerations for HTML Rendering (Browsers Limitations).

The HTML5 Report Viewer's styles are messed or there is a JavaScript 'undefined' error .

Errors on loading CSS, JS files can be seen in the browser's Console. Inspecting the rendered HTML will give you more details if external CSS and JavaScript causes issues in the page. Relative paths may need adjustment - ASP.NET Web Project Paths.

In general, the page with the HTML5 Viewer must load only once jQUERY of version greater than 1.9.1, considered with Telerik Kendo UI JavaScript requirements, and there must be linked Telerik Kendo UI CSS and JS files of the same version - HTML5 Viewer Requirements.

The HTML5 Report Viewer does not display a report specified via InstanceReportSource.

The HTML5 Viewer is an HTML/CSS/JS widget, which gets content produced on the server by the Reporting REST service. Data objects and report instances cannot be submitted to the server in a request. Details how to use an InstanceReportSource with the HTML5 Viewer are avaialble in the How to display a report via InstanceReportSource in the HTML5 Viewer KB article.

The HTML5 WebForms Report Viewer does not work in an AJAXified page.

The HTML5 WebForms ReportViewer is a wrapper of the HTML5 JavaScript Viewer. The wrapper renders the JavaScript object in the page and registers scipts at the end of the page. To update the viewer in the page, you can use its exposed Client-Side API or you can make a full post-back to recreate the viewer object.

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