Dim selectedItem As New Style(GetType(DataGridCell))
    Dim triggerIsSelected As New Trigger() With {.[Property] = DataGridCell.IsSelectedProperty, .Value = True}
    triggerIsSelected.Setters.Add(New Setter(DataGridCell.BackgroundProperty, System.Windows.Media.Color.Red))
    selectedItem.Triggers.Add(triggerIsSelected)
    Datagrid1.CellStyle = selectedItem