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IEqualityComparer的使用
当我们用Linq操作我们自定义的对像数组时，我们会发现有些方法直接使用的话根本不起作用，比如：Distinct、Except、Intersect等扩展方法。
对于我们自定义的对象的比较，我们必须实现IEqualityComparer接口来判断两个对象的相等性。
示例代码如下：
using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace lambda{ class Program { static void Main(string[] args) { Park p1 = new Park { ticketPrice = 55, address = "南京", peoples = 85 }; Park p2 = new Park { ticketPrice = 85, address = "北京", peoples = 75 }; Park p3 = new Park { ticketPrice = 78, address = "多伦多", peoples = 100 }; List<Park> parks = new List<Park>(){ new Park { ticketPrice = 11, address = "天堂", peoples = 1000 }, new Park { ticketPrice = 11, address = "天堂", peoples = 1000 } }; parks.Add(p1); parks.Add(p2); parks.Add(p3); var diff = from c in parks.Distinct(new Park()) select c; foreach (var item in diff) { Console.WriteLine(item.address); } } } class Park : IEqualityComparer<Park> { public double ticketPrice { get; set; } public string address { get; set; } public int peoples { get; set; } public bool Equals(Park x, Park y) //比较x和y对象是否相同，按照地址比较 { return x.address == y.address; } public int GetHashCode(Park obj) { return obj.ToString().GetHashCode(); } }}
或者将比较器单独写成一个类也可以，更多详细信息参见以下链接：
http://msdn.microsoft.com/zh-cn/library/ms132151.aspx
using System;using System.Collections.Generic;class Example{ static void Main() { try { BoxEqualityComparer boxEqC = new BoxEqualityComparer(); Dictionary<Box, String> boxes = new Dictionary<Box, string>(boxEqC); Box redBox = new Box(4, 3, 4); Box blueBox = new Box(4, 3, 4); boxes.Add(redBox, "red"); boxes.Add(blueBox, "blue"); Console.WriteLine(redBox.GetHashCode()); Console.WriteLine(blueBox.GetHashCode()); } catch (ArgumentException argEx) { Console.WriteLine(argEx.Message); } }}public class Box{ public Box(int h, int l, int w) { this.Height = h; this.Length = l; this.Width = w; } public int Height { get; set; } public int Length { get; set; } public int Width { get; set; }}class BoxEqualityComparer : IEqualityComparer<Box>{ public bool Equals(Box b1, Box b2) { if (b1.Height == b2.Height & b1.Length == b2.Length & b1.Width == b2.Width) { return true; } else { return false; } } public int GetHashCode(Box bx) { int hCode = bx.Height ^ bx.Length ^ bx.Width; return hCode.GetHashCode(); }}
IEqualityComparer的使用
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