WPF CollapsibleRowDefinition, CollapsibleColumnDefinition

Collapsible.cs

using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;

namespace Controls
{
    /// <summary>
    /// <see cref="RowDefinition"/> implementation that supports a collapsed state.
    /// </summary>
    /// <remarks>
    /// A <c>RowDefinition</c>, when used with a <see cref="GridSplitter"/>, can produce undesired behavior if the row needs to be
    /// collapsible. That is, the row needs to support a collapsed state, possibly to be invisible or with a minimum height. This class
    /// can be used for this purpose with separate heights specified for both the collapsed and expanded states.
    /// </remarks>
    /// <example>
    /// <code><![CDATA[
    ///   <Grid.RowDefinitions>
    ///       <controls:CollapsibleRowDefinition CollapsedHeight="0" ExpandedHeight="500" IsExpanded="{Binding HeaderVisible}"/>
    ///       <RowDefinition Height="Auto"/>
    ///       <RowDefinition Height="*"/>
    ///   </Grid.RowDefinitions>
    /// ]]></code>
    /// </example>
    /// <seealso cref="System.Windows.Controls.RowDefinition" />
    /// <seealso cref="CollapsibleColumnDefinition"/>
    public class CollapsibleRowDefinition : RowDefinition
    {
        // NOTE: Inspired by https://stackoverflow.com/a/33640443/84522

        /// <summary>
        /// The property that indicates whether the row is expanded
        /// </summary>
        public static readonly DependencyProperty IsExpandedProperty = DependencyProperty.Register(
            "IsExpanded",
            typeof(bool),
            typeof(CollapsibleRowDefinition),
            new FrameworkPropertyMetadata(
                false,
                (s, e) => { ((CollapsibleRowDefinition)s).IsExpanded = (bool)e.NewValue; }));

        private bool _isExpanded;

        /// <summary>
        /// Initializes a new instance of the <see cref="CollapsibleRowDefinition"/> class.
        /// </summary>
        public CollapsibleRowDefinition()
        {
            DependencyPropertyDescriptor.FromProperty(
                HeightProperty,
                typeof(RowDefinition)).AddValueChanged(
                    this,
                    (sender, args) =>
                    {
                        if (IsExpanded)
                        {
                            ExpandedHeight = Height;
                        }
                    });
        }

        /// <summary>
        /// Gets or sets the collapsed height of the row.
        /// </summary>
        public GridLength CollapsedHeight { get; set; }

        /// <summary>
        /// Gets or sets the expanded height of the row.
        /// </summary>
        public GridLength ExpandedHeight { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether the row is expanded
        /// </summary>
        public bool IsExpanded
        {
            get => _isExpanded;
            set
            {
                if (_isExpanded == value)
                {
                    return;
                }

                _isExpanded = value;
                Height = _isExpanded ? ExpandedHeight : CollapsedWidth;
            }
        }
    }

    /// <summary>
    /// <see cref="ColumnDefinition"/> implementation that supports a collapsed state.
    /// </summary>
    /// <remarks>
    /// A <c>ColumnDefinition</c>, when used with a <see cref="GridSplitter"/>, can produce undesired behavior if the column needs to be
    /// collapsible. That is, the column needs to support a collapsed state, possibly to be invisible or with a minimum width. This class
    /// can be used for this purpose with separate widths specified for both the collapsed and expanded states.
    /// </remarks>
    /// <example>
    /// <code><![CDATA[
    ///   <Grid.ColumnDefinitions>
    ///       <controls:CollapsibleColumnDefinition CollapsedWidth="0" ExpandedWidth="500" IsExpanded="{Binding HeaderVisible}"/>
    ///       <ColumnDefinition Width="Auto"/>
    ///       <ColumnDefinition Width="*"/>
    ///   </Grid.ColumnDefinitions>
    /// ]]></code>
    /// </example>
    /// <seealso cref="System.Windows.Controls.ColumnDefinition" />
    /// <seealso cref="CollapsibleRowDefinition"/>
    public class CollapsibleColumnDefinition : ColumnDefinition
    {
        // NOTE: Inspired by https://stackoverflow.com/a/33640443/84522

        /// <summary>
        /// The property that indicates whether the column is expanded
        /// </summary>
        public static readonly DependencyProperty IsExpandedProperty = DependencyProperty.Register(
            "IsExpanded",
            typeof(bool),
            typeof(CollapsibleColumnDefinition),
            new FrameworkPropertyMetadata(
                false,
                (s, e) => { ((CollapsibleColumnDefinition)s).IsExpanded = (bool)e.NewValue; }));

        private bool _isExpanded;

        /// <summary>
        /// Initializes a new instance of the <see cref="CollapsibleColumnDefinition"/> class.
        /// </summary>
        public CollapsibleColumnDefinition()
        {
            DependencyPropertyDescriptor.FromProperty(
                WidthProperty,
                typeof(ColumnDefinition)).AddValueChanged(
                    this,
                    (sender, args) =>
                    {
                        if (IsExpanded)
                        {
                            ExpandedWidth = Width;
                        }
                    });
        }

        /// <summary>
        /// Gets or sets the collapsed width of the column.
        /// </summary>
        public GridLength CollapsedWidth { get; set; }

        /// <summary>
        /// Gets or sets the expanded width of the column.
        /// </summary>
        public GridLength ExpandedWidth { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether the column is expanded
        /// </summary>
        public bool IsExpanded
        {
            get => _isExpanded;
            set
            {
                if (_isExpanded == value)
                {
                    return;
                }

                _isExpanded = value;
                Width = _isExpanded ? ExpandedWidth : CollapsedWidth;
            }
        }
    }
}