Configure The Filtering Mode
RadGridView has two filtering modes as described in this article.
Popup Filtering Mode
To enable the popup filtering mode, set RadGridView’s FilteringMode property to Popup or do not set anything, since this is the standard default filtering mode.
<telerik:RadGridView FilteringMode="Popup" />
Filter Row Mode
To enable the custom filter row mode, set RadGridView’s FilteringMode property to FilterRow.
<telerik:RadGridView FilteringMode="FilterRow" />
Popup Filtering Mode