public static class GridEx
    {
        public static int GetRowCount(Grid obj) => (int)obj.GetValue(RowCountProperty);
        public static void SetRowCount(Grid obj, int value) => obj.SetValue(RowCountProperty, value);

        public static readonly DependencyProperty RowCountProperty =
            DependencyProperty.RegisterAttached("RowCount", typeof(int), typeof(GridEx), new PropertyMetadata(0, OnRowsChanged));

        public static string GetRowHeights(Grid obj) => (string)obj.GetValue(RowHeightsProperty);
        public static void SetRowHeights(Grid obj, string value) => obj.SetValue(RowHeightsProperty, value);

        public static readonly DependencyProperty RowHeightsProperty =
            DependencyProperty.RegisterAttached("RowHeights", typeof(string), typeof(GridEx), new PropertyMetadata("", OnRowsChanged));

        private static void OnRowsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var grid = (Grid)d;
            var rowDefinitions = grid.RowDefinitions;
            var rowCount = GetRowCount(grid);
            var rowHeightsString = GetRowHeights(grid);
            var rowHeights = ParseRowHeightsString(rowHeightsString);
            var rowCountTotal = Math.Max(rowCount, rowHeights.Length);
            if (rowDefinitions.Count > rowCountTotal)
                rowDefinitions.RemoveRange(rowCount, rowDefinitions.Count - rowCountTotal);
            for (int i = 0; i < rowHeights.Length; ++i)
            {
                if (rowDefinitions.Count <= i)
                    rowDefinitions.Add(new RowDefinition { Height = rowHeights[i] });
                if (rowDefinitions[i].Height != rowHeights[i])
                    rowDefinitions[i].Height = rowHeights[i];
            }
            while (rowDefinitions.Count < rowCount)
                rowDefinitions.Add(new RowDefinition());
        }

        private static GridLength[] ParseRowHeightsString(string rowHeightsString)
        {
            var parts = rowHeightsString.ToUpper()
                            .Split(" ,".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
            var gridLengths = new GridLength[parts.Length];
            for (int i = 0; i < parts.Length; ++i)
            {
                if (parts[i] == "AUTO") continue;
                int endSymbolIndex = parts[i].Length - 1;
                if (parts[i][endSymbolIndex] == '*')
                {
                    double value = 1;
                    if (parts[i].Length > 1
                        && !double.TryParse(parts[i].Substring(0, endSymbolIndex), out value))
                            throw new ArgumentException("Illegal argument RowHeights");
                    gridLengths[i] = new GridLength(value, GridUnitType.Star);
                    continue;
                }
                if (!double.TryParse(parts[i], out var pixels))
                    throw new ArgumentException("Illegal argument RowHeights");
                gridLengths[i] = new GridLength(pixels);
            }
            return gridLengths;
        }
    }