Automatically set Grid.Rows and Grid.Columns for children controls of a Grid

GridAssist.cs

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

namespace HowToBetterUtilizeGrid;

static class GridAssist
{
    #region AutoRowColumn

    public static string GetAutoRowColumn(DependencyObject obj)
    {
        return (string)obj.GetValue(AutoRowColumnProperty);
    }

    public static void SetAutoRowColumn(DependencyObject obj, string value)
    {
        obj.SetValue(AutoRowColumnProperty, value);
    }

    /// <summary>
    /// 自动排列 Grid 容器中的所有控件
    /// </summary>
    /// <remarks>
    /// 值为一个逗号隔开的字符串，形如：<br/>
    /// - 2,3（2 行 3 列，列宽默认为 1*，行高为 Auto）<br/>
    /// - _,3（3 列，行数根据子控件而定）<br/>
    /// - 2,3,Auto（列的宽度为 Auto）<br/>
    /// Grid 中的所有控件将自动按照从左到右、从上到下的顺序进行排列<br/>
    /// 控件各自的 RowSpan 以及 ColumnSpan 也会被考虑
    /// </remarks>
    /// <example>
    /// <code>
    /// <![CDATA[
    /// <Window xmlns:ap="clr-namespace:NemoDemo.AttachedProperties">
    ///     <Grid ap:GridHelper.AutoRowColumn="2,3">
    ///         <Button />                     // 1,1
    ///         <Label />                      // 1,2
    ///         <TextBox />                    // 1,3
    ///         <Button />                     // 2,1
    ///         <Label Grid.ColumnSpan="2" />  // 2,2-3
    ///     </Grid>
    /// </Window>
    /// ]]>
    /// </code>
    /// </example>
    public static readonly DependencyProperty AutoRowColumnProperty = DependencyProperty.RegisterAttached(
        "AutoRowColumn",
        typeof(string),
        typeof(GridAssist),
        new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.AffectsMeasure, OnAutoRowColumnChanged)
    );

    private static void OnAutoRowColumnChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (!(d is Grid grid))
            return;

        var value = e.NewValue as string;
        if (string.IsNullOrEmpty(value))
        {
            grid.RowDefinitions.Clear();
            grid.ColumnDefinitions.Clear();

            grid.Loaded -= OnGridLoaded;
            return;
        }

        grid.Loaded += OnGridLoaded;

        if (grid.IsLoaded)
            OnGridLoaded(grid, null);
    }

    private static void OnGridLoaded(object sender, RoutedEventArgs e)
    {
        var grid = sender as Grid;

        // 列宽，默认为 Star，即平均分布
        var width = new GridLength(1.0, GridUnitType.Star);
        var split = GridAssist.GetAutoRowColumn(grid).Split(',');
        var r = split[0] != "_" ? int.Parse(split[0]) : 1;
        var c = int.Parse(split[1]);
        // 如果有第三个参数且值为 auto，则宽度为 Auto
        if (split.Length == 3 && split[2].Equals("auto", StringComparison.OrdinalIgnoreCase))
            width = GridLength.Auto;
        grid.RowDefinitions.Clear();
        grid.ColumnDefinitions.Clear();
        for (int i = 0; i < r; i++)
            grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto });
        for (int i = 0; i < c; i++)
            grid.ColumnDefinitions.Add(new ColumnDefinition { Width = width });

        var cols = grid.ColumnDefinitions.Count;

        var map = new List<bool[]>();

        int x = 0,
            y = 0;
        foreach (UIElement item in grid.Children)
        {
            var rowSpan = Grid.GetRowSpan(item);
            var colSpan = Grid.GetColumnSpan(item);

            // 默认从上到下，从左到右，即任何时候控件的下方和右方都是空的
            // 可能会出现中途有一个 RowSpan > 1 导致其左下方的右侧不为空的情况，暂不处理
            // 同时默认当前的 (x, y) 位置是一个可用位置

            // 当前控件占据的格子
            for (int i = 0; i < rowSpan; i++)
            {
                // 如果 RowDefinition 不够用，则自动添加
                if (map.Count <= y + i)
                {
                    while (map.Count <= y + i)
                    {
                        grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto });
                        map.Add(new bool[cols]);
                    }
                }

                map[y + i][x] = true;
            }

            for (int i = 0; i < colSpan; i++)
            {
                if (x + i >= cols)
                    break;
                map[y][x + i] = true;
            }

            Grid.SetRow(item, y);
            Grid.SetColumn(item, x);

            // 寻找下一个可用的格子
            while (map[y][x])
            {
                x++;
                if (x >= cols)
                {
                    x = 0;
                    y++;
                    if (y >= map.Count)
                    {
                        grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto });
                        map.Add(new bool[cols]);
                    }
                }
            }
        }
    }

    #endregion
}