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：