Until released the text can be cleared this way:
GridSearchCellElement searchCell = this.radGridView1.TableElement.FindDescendant<GridSearchCellElement>();
Hello,
this.radGridView1.MasterView.TableSearchRow.Search(null);
This used to work in older versions. The actual issue is that if one use the Search method of the row, the query text was not synced with the text box at all.
A fix will be available in Telerik UI for WinForms version R1 2019 SP1.
Regards,
Dimitar