C#动态数据集合ObservableCollection的三种排序方式

WPF中对ListBox、ListView、TreeView等实现数据双向绑定经常会用到ObservableCollection 类。

ObservableCollection 类    表示一个动态数据集合，它是实现了INotifyPropertyChanged 接口的数据集合，在添加项、移除项或刷新整个列表时，此集合将提供通知。如果要实现集合中的某字段或属性发生改变时通知UI刷新界面，我们需要为这些字段或属性实现INotifyPropertyChanged接口，此接口公开CollectionChanged事件，只要基础集合发生更改，都能引发该事件。ObservableCollection 类 的使用可以参考博客：https://www.cnblogs.com/santian/p/4366832.html，这里不做过多讲解。

ObservableCollection没有自带的sort排序功能，而实际使用时我们经常需要对数据集合进行排序后再显示，比如按照ID从小到大排序，或者按照禁用状态排序（可用的排在前面）等等。下面新建一个控制台应用程序SortDemo：

1、新建商品类Goods

//商品类
public class Goods
{
    public int Order { get; set; }
    public string Name { get; set; }
    public bool IsSoldOut { get; set; }
}

2、第一种排序方式

ocGoods = new ObservableCollection(ocGoods.OrderByDescending(item => item.IsSoldOut));

程序代码：

static void Main(string[] args)
{
    ObservableCollection ocGoods = new ObservableCollection();
    ocGoods.Add(new Goods() { Order = 1, Name = "钢笔", IsSoldOut = true });
    ocGoods.Add(new Goods() { Order = 2, Name = "羽毛球", IsSoldOut = false });
    ocGoods.Add(new Goods() { Order = 3, Name = "毛巾", IsSoldOut = false });
    ocGoods.Add(new Goods() { Order = 4, Name = "零食", IsSoldOut = true });

    //按照IsSoldOut降序排列，即true在前面
    ocGoods = new ObservableCollection(ocGoods.OrderByDescending(item => item.IsSoldOut));
    foreach (Goods item in ocGoods)
    {
        Console.WriteLine("Order:{0}  Name:{1}  IsSoldOut:{2}", item.Order, item.Name, item.IsSoldOut.ToString());
    }
    Console.ReadLine();
}

结果： 

2、第二种排序方式

自己写一个Sort扩展方法：

public static class ObservableExtension
{
    public static void Sort(this ObservableCollection collection) where T : IComparable
    {
        List sortedList = collection.OrderByDescending(x => x).ToList();//这里用降序
        for (int i = 0; i < sortedList.Count(); i++)
        {
            collection.Move(collection.IndexOf(sortedList[i]), i);
        }
    }
}

调用的时候报错： 

原来是Goods类没有实现IComparable接口，修改Goods类：

//商品类
public class Goods : IComparable
{
    public int Order { get; set; }
    public string Name { get; set; }
    public bool IsSoldOut { get; set; }

    public int CompareTo(Goods other)
    {
        return this.IsSoldOut.CompareTo(other.IsSoldOut);
    }
}

程序代码：

namespace SortDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            ObservableCollection ocGoods = new ObservableCollection();
            ocGoods.Add(new Goods() { Order = 1, Name = "钢笔", IsSoldOut = true });
            ocGoods.Add(new Goods() { Order = 2, Name = "羽毛球", IsSoldOut = false });
            ocGoods.Add(new Goods() { Order = 3, Name = "毛巾", IsSoldOut = false });
            ocGoods.Add(new Goods() { Order = 4, Name = "零食", IsSoldOut = true });

            ocGoods.Sort();//第二种方法

            foreach (Goods item in ocGoods)
            {
                Console.WriteLine("Order:{0}  Name:{1}  IsSoldOut:{2}", item.Order, item.Name, item.IsSoldOut.ToString());
            }
            Console.ReadLine();
        }
    }

    //商品类
    public class Goods : IComparable
    {
        public int Order { get; set; }
        public string Name { get; set; }
        public bool IsSoldOut { get; set; }

        public int CompareTo(Goods other)
        {
            return this.IsSoldOut.CompareTo(other.IsSoldOut);
        }
    }

    public static class ObservableExtension
    {
        public static void Sort(this ObservableCollection collection) where T : IComparable
        {
            List sortedList = collection.OrderByDescending(x => x).ToList();//这里用降序
            for (int i = 0; i < sortedList.Count(); i++)
            {
                collection.Move(collection.IndexOf(sortedList[i]), i);
            }
        }
    }
}

3、第三种排序方式

第二种方式的实质是使用List的特性，那么如果直接用List的Sort排序特性，则不用单独再实现IComparable接口。这里的思路是建一个List列表，Sort后赋值给ObservableCollection，代码：

static void Main(string[] args)
{
    List goodsList = new List();
    goodsList.Add(new Goods() { Order = 1, Name = "钢笔", IsSoldOut = true });
    goodsList.Add(new Goods() { Order = 2, Name = "羽毛球", IsSoldOut = false });
    goodsList.Add(new Goods() { Order = 3, Name = "毛巾", IsSoldOut = false });
    goodsList.Add(new Goods() { Order = 4, Name = "零食", IsSoldOut = true });
    goodsList.Sort(delegate (Goods b1, Goods b2) { return Comparer.Default.Compare(b2.IsSoldOut, b1.IsSoldOut); });

    ObservableCollection ocGoods = new ObservableCollection(goodsList);
    foreach (Goods item in ocGoods)
    {
        Console.WriteLine("Order:{0}  Name:{1}  IsSoldOut:{2}", item.Order, item.Name, item.IsSoldOut.ToString());
    }
    Console.ReadLine();
}