<Grid>
    <TextBlock x:Name="searchTextBlock"
               HorizontalAlignment="Center"
               VerticalAlignment="Center"
               FontFamily="微软雅黑"
               FontSize="24">
        <TextBlock.Triggers>
            <EventTrigger RoutedEvent="TextBlock.Loaded">
                <BeginStoryboard>
                    <Storyboard>
                        <StringAnimationUsingKeyFrames Duration="0:0:1.6"
                                                       RepeatBehavior="Forever"
                                                       Storyboard.TargetName="searchTextBlock"
                                                       Storyboard.TargetProperty="(TextBlock.Text)">
                            <DiscreteStringKeyFrame KeyTime="0:0:0" Value="正在查询" />
                            <DiscreteStringKeyFrame KeyTime="0:0:0.4" Value="正在查询." />
                            <DiscreteStringKeyFrame KeyTime="0:0:0.8" Value="正在查询.." />
                            <DiscreteStringKeyFrame KeyTime="0:0:1.2" Value="正在查询..." />
                        </StringAnimationUsingKeyFrames>
                    </Storyboard>
                </BeginStoryboard>
            </EventTrigger>
        </TextBlock.Triggers>
    </TextBlock>
</Grid>