需要在Linq 中对比两个对象是否相等.
/// <summary>
/// 定义一个点
/// </summary>
class Point
{
public int x { get; set; }
public int y { get; set; }
public Point(int x, int y)
{
this.x = x;
this.y = y;
}
}
List<Point> list1 = new List<Point>() { new Point(1,1), new Point(1, 2), new Point(1, 3), new Point(1, 4), new Point(1, 5), new Point(1, 6)};
var result1 = list1.Where(M => M == new Point(1, 3));
用另外三种对比方法均不能,如下
Point p1 = new Point(2, 1);
Point p2 = new Point(2, 1);
Console.WriteLine(p1 == p2);//False
Console.WriteLine(p1.Equals(p2));//False
// ReferenceEquals 方法用于对象的引用是否相等
// ReferenceEquals 不能重写 注意
Console.WriteLine(System.Object.ReferenceEquals(p1, p2));//False
p1 = p2;
Console.WriteLine(System.Object.ReferenceEquals(p1, p2));//True
由于没有重写 == 运算符 和 Equals 方法,不能够 直接使用否则对比的将是对象的引用地址
需要对类进行重写,详细如下
/// <summary>
/// 定义一个点,并重写对象与对象是否相等的方法
/// 可用于判断对象是否相等
/// eg:
/// obj1 == obj2
/// obj1.Equals(obj2)
/// </summary>
class TestPoint : IEquatable<TestPoint>
{
public int x { get; set; }
public int y { get; set; }
public TestPoint(int x, int y)
{
this.x = x;
this.y = y;
}
/// <summary>
/// 重载 == 运算符
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
/// <returns></returns>
public static bool operator ==(TestPoint p1, TestPoint p2)
{
return (p1.x == p2.x) && (p1.y == p2.y);
}
/// <summary>
/// 重载 != 运算符
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
/// <returns></returns>
public static bool operator !=(TestPoint p1, TestPoint p2)
{
return (p1.x != p2.x) || (p1.y != p2.y);
}
/// <summary>
/// 重写Equals(object obj)
/// </summary>
/// <param name="obj"></param>
/// <returns></returns>
public override bool Equals(object obj)
{
return this.Equals(obj as TestPoint);
}
/// <summary>
/// 重写 计算对象的哈希值方法(自定义 这里只是示范)
/// 该方法用于判断对象的哈希值是否相等 如对象哈希值相同 就认为两个对象 相等
/// </summary>
/// <returns></returns>
public override int GetHashCode()
{
return this.x.GetHashCode() + this.y.GetHashCode();
}
/// <summary>
/// 继承定义Equals<T>方法
/// 需要继承接口IEquatable<T>
/// </summary>
/// <param name="other"></param>
/// <returns></returns>
public bool Equals(TestPoint other)
{
return (this.x == other.x) && (this.y == other.y);
}
}
使用大概示范
Point p1 = new Point(2, 1);
Point p2 = new Point(2, 1);
Console.WriteLine(p1 == p2);//False
Console.WriteLine(p1.Equals(p2));//False
// ReferenceEquals 方法用于对象的引用是否相等
// ReferenceEquals 不能重写 注意
Console.WriteLine(System.Object.ReferenceEquals(p1, p2));//False
p1 = p2;
Console.WriteLine(System.Object.ReferenceEquals(p1, p2));//True
TestPoint p3 = new TestPoint(2, 1);
TestPoint p4 = new TestPoint(2, 1);
Console.WriteLine(p3 == p4);//True
Console.WriteLine(p3.Equals(p4));//True
// ReferenceEquals 方法用于对象的引用是否相等
// ReferenceEquals 不能重写 注意
Console.WriteLine(System.Object.ReferenceEquals(p3, p4));//False
p3 = p4;
Console.WriteLine(System.Object.ReferenceEquals(p3, p4));//True
List<Point> list1 = new List<Point>() { new Point(1,1), new Point(1, 2), new Point(1, 3), new Point(1, 4), new Point(1, 5), new Point(1, 6)};
var result1 = list1.Where(M => M == new Point(1, 3));
List<TestPoint> list2 = new List<TestPoint>() { new TestPoint(1, 1), new TestPoint(1, 2), new TestPoint(1, 3), new TestPoint(1, 4), new TestPoint(1, 5), new TestPoint(1, 6) };
var result2 = list2.Where(M => M == new TestPoint(1, 3));
完整代码如下:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication1
{
/// <summary>
/// 定义一个点
/// </summary>
class Point
{
public int x { get; set; }
public int y { get; set; }
public Point(int x, int y)
{
this.x = x;
this.y = y;
}
}
/// <summary>
/// 定义一个点,并重写对象与对象是否相等的方法
/// 可用于判断对象是否相等
/// eg:
/// obj1 == obj2
/// obj1.Equals(obj2)
/// </summary>
class TestPoint : IEquatable<TestPoint>
{
public int x { get; set; }
public int y { get; set; }
public TestPoint(int x, int y)
{
this.x = x;
this.y = y;
}
/// <summary>
/// 重载 == 运算符
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
/// <returns></returns>
public static bool operator ==(TestPoint p1, TestPoint p2)
{
return (p1.x == p2.x) && (p1.y == p2.y);
}
/// <summary>
/// 重载 != 运算符
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
/// <returns></returns>
public static bool operator !=(TestPoint p1, TestPoint p2)
{
return (p1.x != p2.x) || (p1.y != p2.y);
}
/// <summary>
/// 重写Equals(object obj)
/// </summary>
/// <param name="obj"></param>
/// <returns></returns>
public override bool Equals(object obj)
{
return this.Equals(obj as TestPoint);
}
/// <summary>
/// 重写 计算对象的哈希值方法(自定义 这里只是示范)
/// </summary>
/// <returns></returns>
public override int GetHashCode()
{
return this.x.GetHashCode() + this.y.GetHashCode();
}
/// <summary>
/// 继承定义Equals<T>方法
/// 需要继承接口IEquatable<T>
/// </summary>
/// <param name="other"></param>
/// <returns></returns>
public bool Equals(TestPoint other)
{
return (this.x == other.x) && (this.y == other.y);
}
}
class Program
{
static void Main(string[] args)
{
Point p1 = new Point(2, 1);
Point p2 = new Point(2, 1);
Console.WriteLine(p1 == p2);//False
Console.WriteLine(p1.Equals(p2));//False
// ReferenceEquals 方法用于对象的引用是否相等
// ReferenceEquals 不能重写 注意
Console.WriteLine(System.Object.ReferenceEquals(p1, p2));//False
p1 = p2;
Console.WriteLine(System.Object.ReferenceEquals(p1, p2));//True
TestPoint p3 = new TestPoint(2, 1);
TestPoint p4 = new TestPoint(2, 1);
Console.WriteLine(p3 == p4);//True
Console.WriteLine(p3.Equals(p4));//True
// ReferenceEquals 方法用于对象的引用是否相等
// ReferenceEquals 不能重写 注意
Console.WriteLine(System.Object.ReferenceEquals(p3, p4));//False
p3 = p4;
Console.WriteLine(System.Object.ReferenceEquals(p3, p4));//True
List<Point> list1 = new List<Point>() { new Point(1,1), new Point(1, 2), new Point(1, 3), new Point(1, 4), new Point(1, 5), new Point(1, 6)};
var result1 = list1.Where(M => M == new Point(1, 3));
List<TestPoint> list2 = new List<TestPoint>() { new TestPoint(1, 1), new TestPoint(1, 2), new TestPoint(1, 3), new TestPoint(1, 4), new TestPoint(1, 5), new TestPoint(1, 6) };
var result2 = list2.Where(M => M == new TestPoint(1, 3));
Console.Read();
}
}
}
ReferenceEquals 不能重写 注意。
注意:这里的对象是引用类对象。