Thank you for writing.
The reason for the observed behavior is the fact that the rows with their correct order after performing sorting/filtering/grouping are placed in the ChildRows collection of RadGridView, and not in the Rows collection of the control. Detailed explanation of both collections, can be found in the following help article: http://www.telerik.com/help/winforms/gridview-rows-rows-vs-childrows.html
A bit off topic, I would like to remind you that your subscription package has expired, which means that you are no longer entitled for our support services. I would highly recommend upgrading your license to the latest version in order to continue getting product updates and uninterrupted support services. Please, contact firstname.lastname@example.org
or visit your account for your upgrading options.
I hope that you find this information helpful.
the Telerik team
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