TRDP reports are XML report definitions packaged in a zip archive (could be also plain legacy format TRDX). Those report can be opened with Standalone Report Designer
which is desktop application we provide for end-users.
.NET type report definitions (.CS or .VB files) are created by Visual Studio Report Designer
Only TRDP(TRDX)format can be stored on Telerik Report Server
The main differences between those two formats are also described in this help article
The conversion is possible both ways:
Report templates are available in both Designers (Report Wizards) where in Standalone Designer you can also design and save your custom templates (Report Templates).
I hope this information will help.
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