WPF TextBolck Tooltip 设置

 <TextBlock TextTrimming="CharacterEllipsis" Text="{Binding Path=MemoName}"
            TextAlignment="Left" VerticalAlignment="Center">
            <TextBlock.ToolTip>
                 <TextBlock Text="{Binding MemoName}" MaxWidth="500" TextWrapping="Wrap" />
            </TextBlock.ToolTip>
 </TextBlock>