带有MVVM的WPF DataGrid行样式

我有一个DataGrid，如果ViewModel类的某个属性设置为true，我想在其中更改行边界颜色或背景。我在将DataTrigger绑定到行源项（ViewModel）属性时遇到问题。在这种情况下，我希望绑定到ViewModel属性IsExpired。不幸的是，它不允许我在运行时抛出和异常。如有任何帮助，我们将不胜感激。

public class ViewModel 
{
    public uint Id { get; private set;}
    public string Symbol { get; private set;}
    public bool IsExpired { get; private set;}
}
public class WindowViewModel : PropertyChangedNotifier
{
    public ObservableCollection<ViewModel> ViewModels { get; private set;}
    private DateTime _timestamp;
    public DateTime TimeStamp
    {
        get { return _timestamp; }
        set 
        {
            _timestamp = value;
            OnPropertyChanged("TimeStamp");
        }
    }
}
<Grid x:Name="Layout" d:DataContext="{StaticResource DesignerViewModel}" DataContext="{Binding}">
    <Grid.RowDefinitions>
        <RowDefinition Height="30"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <StackPanel Grid.Row="0" Orientation="Horizontal">
        <TextBlock Text="Accounts" VerticalAlignment="Center" Margin="5"/>
        <ComboBox x:Name="AccountsComboBox" ItemsSource="{Binding Accounts}"  DisplayMemberPath="ClearingNumber" Width="125" 
                  HorizontalAlignment="Left" Margin="5" IsEditable="False" IsReadOnly="True" Style="{StaticResource AccountComboBoxStyle}"/>
        <Button x:Name="LoadPositionsButton" Content="Load" Margin="5" VerticalAlignment="Center" HorizontalAlignment="Center" Width="50" Click="LoadPositionsButtonOnClick"/>
        <TextBlock x:Name="TimeStampTextBlock" HorizontalAlignment="Right" Margin="5" Width="150" Text="{Binding LastUpdate, Converter={StaticResource TimeStampConverter}}"/>
    </StackPanel>
    <DataGrid Grid.Row="1" ItemsSource="{Binding ViewModels}" CanUserAddRows="False" CanUserDeleteRows="False" CanUserReorderColumns="False" CanUserResizeColumns="False"
              CanUserResizeRows="False" CanUserSortColumns="False" AutoGenerateColumns="False" HeadersVisibility="Column">
        <DataGrid.RowStyle>
            <Style TargetType="{x:Type DataGridRow}">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding IsExpired}" Value="True">
                        <Setter Property="BorderBrush" Value="Red"/>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </DataGrid.RowStyle>    
        <!-- ... -->
        <DataGrid.Columns>
            <DataGridTemplateColumn Header="Account">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate DataType="vm:ViewModel">
                        <TextBlock Text="{Binding Account}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>
            <!--<DataGridTemplateColumn Header="Exch">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate DataType="vm:ViewModel">
                        <TextBlock Text="{Binding ExchangeCode}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>-->
            <DataGridTemplateColumn Header="Symbol">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate DataType="vm:ViewModel">
                        <TextBlock Text="{Binding Symbol}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>
            <DataGridTemplateColumn Header="Description">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate DataType="vm:ViewModel">
                        <TextBlock Text="{Binding Description}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>
            <DataGridTemplateColumn Header="Maturity">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate DataType="vm:ViewModel">
                        <TextBlock Text="{Binding MaturityMonthYear}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>
       <DataGrid.Columns>
    </DataGrid>
</Grid>