c# 动态数据集合ObservableCollection

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

ObservableCollection<T> 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<T> 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<Goods>(ocGoods.OrderByDescending(item => item.IsSoldOut));

程序代码：

 1 static void Main(string[] args)
 2 {
 3 ObservableCollection<Goods> ocGoods = new ObservableCollection<Goods>();
 4 ocGoods.Add(new Goods() { Order = 1, Name = "钢笔", IsSoldOut = true });
 5 ocGoods.Add(new Goods() { Order = 2, Name = "羽毛球", IsSoldOut = false });
 6 ocGoods.Add(new Goods() { Order = 3, Name = "毛巾", IsSoldOut = false });
 7 ocGoods.Add(new Goods() { Order = 4, Name = "零食", IsSoldOut = true });
 8 
 9 //按照IsSoldOut降序排列，即true在前面
10 ocGoods = new ObservableCollection<Goods>(ocGoods.OrderByDescending(item => item.IsSoldOut));
11 foreach (Goods item in ocGoods)
12 {
13 Console.WriteLine("Order:{0} Name:{1} IsSoldOut:{2}", item.Order, item.Name, item.IsSoldOut.ToString());
14 }
15 Console.ReadLine();
16 }

结果：

2、第二种排序方式

自己写一个Sort扩展方法：

 1 public static class ObservableExtension
 2 {
 3 public static void Sort<T>(this ObservableCollection<T> collection) where T : IComparable<T>
 4 {
 5 List<T> sortedList = collection.OrderByDescending(x => x).ToList();//这里用降序
 6 for (int i = 0; i < sortedList.Count(); i++)
 7 {
 8 collection.Move(collection.IndexOf(sortedList[i]), i);
 9 }
10 }
11 }

调用的时候报错：

原来是Goods类没有实现IComparable<Goods>接口，修改Goods类：

/商品类
public class Goods : IComparable<Goods>
{
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<Goods> ocGoods = new ObservableCollection<Goods>();
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<Goods>();//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<Goods>
{
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<T>(this ObservableCollection<T> collection) where T : IComparable<T>
{
List<T> 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<Goods>列表，Sort后赋值给ObservableCollection<Goods>，代码：

static void Main(string[] args)
{
List<Goods> goodsList = new List<Goods>();
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<bool>.Default.Compare(b2.IsSoldOut, b1.IsSoldOut); });

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