本文以实例形式展示了C#判等对象是否相等的常用方法，非常实用，可供大家参考借鉴之用。具体分析如下：

一、判断相等的3个方法

1.实例方法

public virtual bool Equals(object obj) { return RuntimeHelpers.Equals(this, obj); }

2.比较值类型静态方法

public static bool Equals(object objA, object objB) { return ((objA == objB) || (((objA != null) && (objB != null)) && objA.Equals(objB))); }

3.比较引用类型静态方法

public static bool ReferenceEquals(object objA, object objB) { return (objA == objB); }

二、判断引用类型是否相等

class Program { static void Main(string[] args) { Team t1 = new Team("马尔切洛·里皮"); Team t2 = new Team("马尔切洛·里皮"); var result = (t1 == t2); Console.WriteLine(result); result = t1.Equals(t2); Console.WriteLine(result); Console.ReadKey(); } } public class Team { public string _coach = string.Empty; public Team(string coach) { this._coach = coach; } } public struct TeamStruct { public string _coach; public TeamStruct(string coach) { this._coach = coach; } }

运行结果：

false

false

分析：引用类型比较的是引用地址，由于t1和t2指向不同的对象实例，所以dou都返回false。

三、判断值类型是否相等

1.值类型判断方法

派生于System.ValueType，对System.Object中的虚方法Equals(object obj)进行了重写

public override bool Equals(object obj) { if (obj == null) { return false; } RuntimeType type = (RuntimeType) base.GetType(); RuntimeType type2 = (RuntimeType) obj.GetType(); if (type2 != type) //比较两个对象是否是同一类型 { return false; } object a = this; if (CanCompareBits(this)) //对象成员如果存在对于堆的引用返回false { return FastEqualsCheck(a, obj); } //反射获取值类型的所有字段 FieldInfo[] fields = type.GetFields(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance); for (int i = 0; i < fields.Length; i++) //遍历字段，对各个字段进行比较 { object obj3 = ((RtFieldInfo) fields[i]).UnsafeGetValue(a); object obj4 = ((RtFieldInfo) fields[i]).UnsafeGetValue(obj); if (obj3 == null) { if (obj4 != null) { return false; } } else if (!obj3.Equals(obj4)) { return false; } } return true; }

2.用==判断是否相等

static void Main(string[] args) { TeamStruct ts1 = new TeamStruct("马尔切洛·里皮"); TeamStruct ts2 = ts1; var result = (ts1 == ts2); Console.WriteLine(result); Console.ReadKey(); }

出现编译错误。原因是值类型不能用==进行判断。

3.用Equals()实例方法判断是否相等

static void Main(string[] args) { TeamStruct ts1 = new TeamStruct("马尔切洛·里皮"); TeamStruct ts2 = ts1; var result = ts1.Equals(ts2); Console.WriteLine(result); Console.ReadKey(); }

返回true。

可见，如果值类型的字段相等，那就相等。

static void Main(string[] args) { TeamStruct ts1 = new TeamStruct("马尔切洛·里皮"); TeamStruct ts2 = ts1; ts2._coach = "高洪波"; var result = ts1.Equals(ts2); Console.WriteLine(result); Console.ReadKey(); }

返回false,当然，值类型的字段有不相等，就会整个不相等。

4.判断复杂值类型是否相等

即值类型中包含引用类型和值类型。

class Program { static void Main(string[] args) { Team t = new Team("马尔切洛·里皮"); TeamStruct ts = new TeamStruct("马尔切洛·里皮"); NationalTeam nt1 = new NationalTeam(t, ts); NationalTeam nt2 = nt1; var result = nt1.Equals(nt2); Console.WriteLine(result); Console.ReadKey(); } } public class Team { public string _coach = string.Empty; public Team(string coach) { this._coach = coach; } } public struct TeamStruct { public string _coach; public TeamStruct(string coach) { this._coach = coach; } } public struct NationalTeam { public Team _team; public TeamStruct _structTeam; public NationalTeam(Team team, TeamStruct structTeam) { this._team = team; this._structTeam = structTeam; } }

返回true，会遍历比较引用类型成员和值类型成员。在nt1和nt2中，类型为Team的引用类型成员_team指向同一个对象实例， 类型为TeamStruct的值类型成员_structTeam相等，所有整个返回。如下图所示：