Please refer to the attached sample project and follow the steps from the gif file.
1) User does a search operation
2) BackgroundWorker does its task and finishes at some point, then set defaults to select the first result.
3) User selects a different result row.
4) Selected record still indicates and points to the first result.
Me.RadMultiColumnComboBox1.EditorControl.MasterView.TableSearchRow.AutomaticallySelectFirstResult = False