The type initializer for Lock threw an exception error in the HTML5 viewer in an ASP.NET Core application
Environment
| Product | Progress® Telerik® Reporting |
| Project Type | .NET |
Important note
The following article applies to Telerik Reporting versions before R1 2019. It elaborates on how to host the Telerik Reporting REST Service and add an HTML5 Report Viewer in an ASP.NET Core web application.
As of Telerik Reporting R1 2019, we support report rendering runtime targeting .NET Core 2.1+ applications. For more information on how to use reports in a .NET Core application for Windows and Linux platforms, please refer to .NET Core Support help article.
Description
When using the HTML5 report viewer to display reports in a .NET Core application, an error is displayed in the viewer: "Error registering the viewer with the service. An error has occurred. The type initializer for 'Lock' threw an exception."
Solution
Such errors occur when the Telerik Reporting NuGet packages we provide for .NET Core projects are not compatible with the project. The packages are built against the full .NET Framework because the Reporting engine relies on the GDI+ API. Therefore, the packages will not work in the project that targets .NET Core framework as GDI+ is missing there.
If you wish to use the packages in .NET Core project use the following steps for creating the project:
- In the New Project dialog, expand Installed > Visual C# > .NET Core, and select ASP.NET Core Web Application project template. Choose a name for the project and click OK.
- On the New ASP.NET Core Web Application dialog select from the drop downs .NET Framework and ASP.NET Core 2. Next from the list of templates select Web API.
It is important to select .NET Framework from the drop down on the second step as this will set full .NET framework as the target framework of the project.
If the above requirement cannot be met you can add just HTML5 Viewer in the project as it does not require any NuGet packages. Reporting REST service can be hosted separately in a project that targets full .NET framework. HTML5 Viewer will only need the address of the service set as its serviceUrl option.
When the service and the viewer are hosted in different domains it will be required to enable CORS in order to enable communication between the viewer and the service.