wpf ListBox,item两列不等高。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;

namespace XXXXXX
{
public class TwoColumnPanel : Panel
{
/// <summary>
/// 先测量需要多大尺寸，做个申报准备
/// </summary>
/// <param name="constraint">限定的尺寸，比如，规定了width和height</param>
/// <returns></returns>
protected override Size MeasureOverride(Size constraint)
{
//定义预期的宽度和高度
double height = 0, height1 = 0, height2 = 0, width = 0;
UIElement element;
if (Children.Count > 0)
{
element = Children[0];
width = element.DesiredSize.Width*2;
}
//遍历每个元素，计算所需的总尺寸
for (int i = 0; i < Children.Count; i++)
{
element = Children[i];
//按照限定的尺寸测量一下自己，拿镜子找着自己
element.Measure(constraint);
if (i % 2 == 0)
{
height1 += element.DesiredSize.Height;
}
else
{
height2 += element.DesiredSize.Height;
}
}
height = height1 > height2 ? height1 : height2;

//申报，我需要这个尺寸
return new Size(width, height);
}

/// <summary>
/// 排列每个元素
/// </summary>
/// <param name="arrangeBounds">测量的尺寸</param>
/// <returns></returns>
protected override Size ArrangeOverride(Size arrangeBounds)
{
double currentX2 = 0,currentY1 = 0,currentY2 = 0;
UIElement element;

if (Children.Count > 0)
{
element = Children[0];
currentX2 = element.DesiredSize.Width;
}

for (int i = 0; i < Children.Count; i++)
{
element = Children[i];
//排列每个元素
if (i % 2 == 0)
{
Children[i].Arrange(new Rect(0, currentY1, element.DesiredSize.Width, element.DesiredSize.Height));
currentY1 += element.DesiredSize.Height;
}
else
{
Children[i].Arrange(new Rect(currentX2, currentY2, element.DesiredSize.Width, element.DesiredSize.Height));
currentY2 += element.DesiredSize.Height;
}

}
return arrangeBounds;
}
}
}