UWP：行数に基づいてTextBlockのテキストをトリミングする

拡張可能なテキストブロックを作成するためのすべてのステップを説明する良いトピックを読んでください

また、githubでソースコードを表示します

XAMLコードは次のとおりです。

 <Grid x:Name="LayoutRoot" Tapped="LayoutRoot_OnTap">
     <Grid.RowDefinitions>
          <RowDefinition Height = "Auto" />
          <RowDefinition Height="Auto" />
      </Grid.RowDefinitions>

      <TextBlock Grid.Row="0" 
                  x:Name= "CommentTextBlock"
                  HorizontalAlignment= "Left"
                  TextWrapping= "Wrap"
                  Height= "Auto"
                  Width= "280" />

      < StackPanel Grid.Row= "1"
                  Orientation= "Horizontal"
                  HorizontalAlignment= "Right"
                  x:Name= "ExpandHint"
                  Visibility= "Collapsed"
                  Margin= "0,5,0,0" >
          < TextBlock  Text= "View More" />
           < TextBlock Margin= "10,0,10,0"
        Text= "+" />
      </ StackPanel >
</ Grid >

これがC＃の部分です

public sealed partial class ExpandableTextBlock : UserControl
{
   public ExpandableTextBlock()
    {
        this.InitializeComponent();
    }

    public static readonly DependencyProperty TextProperty = DependencyProperty.Register(
        "Text", typeof(string), typeof(ExpandableTextBlock), new PropertyMetadata(default(string), OnTextChanged));

    public string Text
    {
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }

    private static void OnTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var ctl = (ExpandableTextBlock)d;
        ctl.CommentTextBlock.SetValue(TextBlock.TextProperty, (string)e.NewValue);
        ctl.CommentTextBlock.SetValue(TextBlock.HeightProperty, Double.NaN);

        ctl.CommentTextBlock.Measure(new Size(ctl.CommentTextBlock.Width, double.MaxValue));

        double desiredheight = ctl.CommentTextBlock.DesiredSize.Height;
        ctl.CommentTextBlock.SetValue(TextBlock.HeightProperty, (double)63);

        if (desiredheight > (double)ctl.CommentTextBlock.GetValue(TextBlock.HeightProperty))
        {
            ctl.ExpandHint.SetValue(StackPanel.VisibilityProperty, Visibility.Visible);
            ctl.MaxHeight = desiredheight;
        }
        else
        {
            ctl.ExpandHint.SetValue(StackPanel.VisibilityProperty, Visibility.Collapsed);
        }

        //Setting length of comments
        var boundsWidth = Window.Current.Bounds.Width;
        ctl.CommentTextBlock.SetValue(TextBlock.WidthProperty, boundsWidth);
    }

    public static readonly DependencyProperty CollapsedHeightProperty = DependencyProperty.Register(
        "CollapsedHeight", typeof(double), typeof(ExpandableTextBlock), new PropertyMetadata(default(double), OnCollapsedHeightChanged));


    public double CollapsedHeight
    {
        get { return (double)GetValue(CollapsedHeightProperty); }
        set { SetValue(CollapsedHeightProperty, value); }
    }

    private static void OnCollapsedHeightChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var ctl = (ExpandableTextBlock)d;
        ctl.CollapsedHeight = (double)e.NewValue;
    }


    public static readonly DependencyProperty TextStyleProperty = DependencyProperty.Register(
       "TextStyle", typeof(Style), typeof(ExpandableTextBlock), new PropertyMetadata(default(Style), OnTextStyleChanged));

    public Style TextStyle
    {
        get { return (Style)GetValue(TextStyleProperty); }
        set { SetValue(TextStyleProperty, value); }
    }

    private static void OnTextStyleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var ctl = (ExpandableTextBlock)d;
        ctl.CommentTextBlock.SetValue(StyleProperty, (Style)e.NewValue);
    }

    private void LayoutRoot_OnTap(object sender, TappedRoutedEventArgs tappedRoutedEventArgs)
    {
       if ((Visibility)this.ExpandHint.GetValue(StackPanel.VisibilityProperty) == Visibility.Visible)
        {
            //transition
            this.CommentTextBlock.SetValue(TextBlock.HeightProperty, Double.NaN);

            this.ExpandHint.SetValue(StackPanel.VisibilityProperty, Visibility.Collapsed);
        }
    }
}