At present, the RadFileExplorer performance will degrade for folders containing more than 300-400 files. This is possible to improve in the future, and is in our TODO list, but will require substantial effort, as the Grid logic needs to be thoroughly modified. For the time being I do not recommend using the control if the folders you intened to manage are likely to contain more than 300 items.
That said, the biggest "culprit" for slowing things down is usually MS AJAX
debugging code. Please make sure that in your Web.config
file the option <compliation debug="false
"> - this will increase the client-side performance severalfold.
the Telerik team
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