Hello Sasa Grebenar,
It is very complicated and it is hard to reproduce the problem using just a code snippet you sent.
Most often this problem occurs in published projects when MIME types for shape and dbf files are not defined on the web server. Please check that MIME types for using shape files are defined:
Extensions: .shp and .dbf
MIME type: application/octet-stream
The version you use does not fire the PreviewReadCompleted event when an error occurs during loading of shape files. You can use the ReadCompleted event to check the eventArgs.Error property that returns the exception when it occurs.
the Telerik team
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