I have replied you in the support ticket that you opened regarding this question. I will, however, paste my answer here as well, so that it is shared with the community.
If you are using GridViewSelectColumn and refer to the selection of RadGridView being cleared, this would be the expected behavior. The selection is an operation applied over the current view. When an item is filtered, it is cleared from it, thus the selection cannot be automatically persisted.
What I can suggest you is to write some custom code for manually handling this scenario. For achieving this, you can use the Filtering/Filtered events of RadGridView and set the SelectedItem property of the control to be the previously persisted one.
If you need further assistance or have any concerns regarding this topic, please, let us continue the communication in the aforementioned support thread, so that double posting is avoided.
Thanks in advance for understanding.
All the best,
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