1. A custom report template is checked for getting the data source information needed
2. A new empty Telerik report is created
3. The report is client-side filled with those predefined data sources using the Telerik Javascript Shell (EditorCommand.NewItem for creating them and SetPropertyValue for filling in the details).

This approach has been working well for me until getting updated to the R1 2021 SP1 release (15.0.21.224), or the following versions, which are now unable to show the datasources fields in the explorer at first. However, manually adding a new component into the canvas makes the datasource tree to be updated then.

Optimize the Telerik Reporting performance by parallelizing the reporting paging and rendering. Better utilize CPUs with multiple cores and as a result, improve the REST Service throughput and decrease the viewers' rendering times.

When using the Report Viewer under WinForms, Print Preview allows the user to scroll through all report documents.  I.E., everything in the document map.  However, when using the Wpf version you cannot.  In the Wpf version, the user must use the Document map to select and scroll through each particular area.

For large reports containing multiple documents, this is tedious.  

Please make the Print Preview functionality for the WPF control match that supported by the WinForms control.