A panel which arranges it's children into the specified amount of columns and stretches them to uniformly consume the whole width

UniformWidthWrapPanel.cs

using System;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace KodeFisk
{
	public class UniformWidthWrapPanel : Panel
	{
		public UniformWidthWrapPanel()
		{
			MaximumColumns = 1;
		}
		public int MaximumColumns
		{
			get { return (int)GetValue(MaximumColumnsProperty); }
			set { SetValue(MaximumColumnsProperty, value); }
		}

		// Using a DependencyProperty as the backing store for MaximumColumns.  This enables animation, styling, binding, etc...
		public static readonly DependencyProperty MaximumColumnsProperty =
			DependencyProperty.Register("MaximumColumns", typeof(int), typeof(UniformWidthWrapPanel), new PropertyMetadata(null));


		protected override Size MeasureOverride(Size availableSize)
		{
			var finalSize = new Size { Width = availableSize.Width };
			var columnWidth = availableSize.Width / MaximumColumns;

			var rowHeight = 0d;
			var rowChildCount = 0;
			foreach (var child in Children)
			{
				child.Measure(new Size(columnWidth, availableSize.Height));
				if (rowChildCount < MaximumColumns)
				{
					rowHeight = Math.Max(child.DesiredSize.Height, rowHeight);
				}
				else
				{
					finalSize.Height += rowHeight;
					rowHeight = child.DesiredSize.Height;
					rowChildCount = 0;
				}
				rowChildCount++;
			}

			finalSize.Height += rowHeight;
			return finalSize;
		}

		protected override Size ArrangeOverride(Size finalSize)
		{
			var columnWidth = finalSize.Width / MaximumColumns;
			var posY = 0d;

			var rowHeight = 0d;
			var rowChildCount = 0;
			foreach (var child in Children)
			{
				if (rowChildCount >= MaximumColumns)
				{
					rowChildCount = 0;
					posY += rowHeight;
					rowHeight = 0;
				}

				child.Arrange(new Rect(columnWidth * rowChildCount, posY, columnWidth, child.DesiredSize.Height));
				rowHeight = Math.Max(child.DesiredSize.Height, rowHeight);
				rowChildCount++;
			}

			return finalSize;
		}
	}
}