Answer by Sinatr for Is there a simple way to describe a list of equal objects in XAML?

How about using attached properties and syntax like this:

<!-- Define xmlns:b="clr-namespace:Behaviors" --><!-- Create 5 columns: 1/3 width, 2/3 width, auto, auto and 50 pixels --><Grid b:GridBehavior.Columns="1*,2*,,auto,50"> ... </Grid>

Implementation:

using System.ComponentModel;using System.Windows;using System.Windows.Controls;namespace Behaviors;public class GridBehavior : DependencyObject{    public static readonly DependencyProperty ColumnsProperty = DependencyProperty.RegisterAttached("Columns", typeof(string), typeof(GridBehavior), new PropertyMetadata((s, e) =>        {            if (s is not Grid grid)                throw new InvalidOperationException("Must be Grid.");            var converter = TypeDescriptor.GetConverter(typeof(GridLength));            var columns = e.NewValue.ToString()!.Split(",").Select(o =>            {                if (o == "")                    return new ColumnDefinition();                else if (converter.ConvertFromString(o) is GridLength gridLength)                    return new ColumnDefinition { Width = gridLength };                return new ColumnDefinition();            });            grid.ColumnDefinitions.Clear();            foreach (var column in columns)                grid.ColumnDefinitions.Add(column);        }));    public static string GetColumns(DependencyObject obj) => (string)obj.GetValue(ColumnsProperty);    public static void SetColumns(DependencyObject obj, string value) => obj.SetValue(ColumnsProperty, value);}

You can omit verbose xaml to define columns in many cases.

In your specific case the value will be

b:GridBehavior.Columns=",,,,,,,,,,,,,,,,,,,,,,,"

which isn't bad, right?

TODO: multiplier for repeated columns, support GroupName (as suffix #SomeGroupName?), do same for rows.