背景
最近在群里，有人问如何深度比较2个对象相等，感觉很有意思，就自己研究了一下，并写了一个开源的小类库，地址如下https://github.com/lamondlu/ObjectEquality。
如果想直接使用这个类库，可以使用Nuget进行安装
Install-Package ObjectEquality对象比较有几种情况
- 对象是值类型或者String，这里仅需要判断值是否相等
- 对象是Struct，需要判断Struct的每个字段是否一致
- 对象是集合，需要判断对应位置的对象是否相等
- 对象是数组，需要判断对应位置的对象是否相等
- 对象是Class, 需要判断Class的每个字段是否一致
这里可能有缺漏，大家可以帮我补充。
编写代码
这里我首先创建了一个IEquality接口，在其中定义了一个IsEqual方法，这个方法就是判断2个对象是否一致的方法。后面我会针对上面说明的几种对比场景，分别创建对应的实现类。
???public interface IEquality ???{ ???????Func<object, bool> MatchCondition { get; } ???????bool IsEqual(object source, object target); ???}这里MatchCondition是一个委托，它定义了当前对比类的匹配条件。
第二步，我们针对上述的几种对比场景，创建对应的实现类
值类型相等判断实现类
???internal class ValueTypeEquality : IEquality ???{ ???????public Func<object, bool> MatchCondition ???????{ ???????????get ???????????{ ???????????????return p => p.GetType().IsValueType || p.GetType() == typeof(string); ???????????} ???????} ???????public bool IsEqual(object source, object target) ???????{ ???????????return source.Equals(target); ???????} ???}值类型的判断比较简单，直接调用Object类的Equals方法即可。
String类型虽然不是值类型，但是这里我们需要把它归到值类型中。
Struct相等判断实现类
???internal class StructEquality : IEquality ???{ ???????public Func<object, bool> MatchCondition ???????{ ???????????get ???????????{ ???????????????return p => p.GetType().IsValueType ????????????????????&& !p.GetType().IsPrimitive ????????????????????&& !p.GetType().IsEnum; ???????????} ???????} ???????public bool IsEqual(object source, object target) ???????{ ???????????var type = source.GetType(); ???????????foreach (var prop in type.GetProperties()) ???????????{ ???????????????var equality = EqualityCollection.Equalities ???????????????????.First(p => p.MatchCondition(prop.GetValue(source))); ???????????????var result = equality.IsEqual(prop.GetValue(source), ???????????????????prop.GetValue(target)); ???????????????if (!result) ???????????????{ ???????????????????return false; ???????????????} ???????????} ???????????return true; ???????} ???} ??这里我们读取了Struct中的每个属性，分别进行判断，如果有一个判断失败，即认为2个Struct对象不相等。
这里
EqualityCollection是判断器集合，后续会添加这个类的代码。
集合相等判断实现类
???internal class GenericCollectionEquality : IEquality ???{ ???????public Func<object, bool> MatchCondition ???????{ ???????????get ???????????{ ???????????????return p => p.GetType().IsGenericType; ???????????} ???????} ???????public bool IsEqual(object source, object target) ???????{ ???????????var type = source.GetType(); ???????????var genericType = type.GetGenericArguments()[0]; ???????????var genericCollectionType = typeof(IEnumerable<>).MakeGenericType(genericType); ???????????if (type.GetInterfaces().Any(p => p == genericCollectionType)) ???????????{ ???????????????var countMethod = type.GetMethod("get_Count"); ???????????????var sourceCount = (int)countMethod.Invoke(source, null); ???????????????var targetCount = (int)countMethod.Invoke(target, null); ???????????????if (sourceCount != targetCount) ???????????????{ ???????????????????return false; ???????????????} ???????????????var sourceCollection = (source as IEnumerable<object>).ToList(); ???????????????var targetCollection = (target as IEnumerable<object>).ToList(); ???????????????for (var i = 0; i < sourceCount; i++) ???????????????{ ???????????????????var equality = EqualityCollection.Equalities.First(p => p.MatchCondition(sourceCollection[i])); ???????????????????var result = equality.IsEqual(sourceCollection[i], targetCollection[i]); ???????????????????if (!result) ???????????????????{ ???????????????????????return false; ???????????????????} ???????????????} ???????????} ???????????return true; ???????} ???}这里我们首先判断了集合的元素的数量是否一致，如果不一致，即这2个集合不相等。如果一致，我们继续判断对应位置的每个元素是否一致，如果全部都一直，则2个集合相当，否则2个集合不相等。
数组相等判断实现类
???internal class ArrayEquality : IEquality ???{ ???????public Func<object, bool> MatchCondition ???????{ ???????????get ???????????{ ???????????????return p => p.GetType().IsArray; ???????????} ???????} ???????public bool IsEqual(object source, object target) ???????{ ???????????Array s = source as Array; ???????????Array t = target as Array; ???????????if (s.Length != t.Length) ???????????{ ???????????????return false; ???????????} ???????????????????????for (var i = 0; i < s.Length; i++) ???????????{ ???????????????var equality = EqualityCollection.Equalities ???????????????????.First(p => p.MatchCondition(s.GetValue(i))); ???????????????var result = equality.IsEqual(s.GetValue(i), t.GetValue(i)); ???????????????if (!result) ???????????????{ ???????????????????return false; ???????????????} ???????????} ???????????return true; ???????} ???}数组相等的判断类似集合，我们首先判断数组的长度是否一致，然后判断对应位置的元素是否一致。
类判断相等实现类
???internal class ClassEquality : IEquality ???{ ???????public Func<object, bool> MatchCondition ???????{ ???????????get ???????????{ ???????????????return p => p.GetType().IsClass; ???????????} ???????} ???????public bool IsEqual(object source, object target) ???????{ ???????????var type = source.GetType(); ???????????foreach (var prop in type.GetProperties()) ???????????{ ???????????????var equality = EqualityCollection.Equalities ???????????????????.First(p => p.MatchCondition(prop.GetValue(source))); ???????????????var result = equality.IsEqual(prop.GetValue(source), prop.GetValue(target)); ???????????????if (!result) ???????????????{ ???????????????????return false; ???????????????} ???????????} ???????????return true; ???????} ???}添加判断相等实现类集合
???public static class EqualityCollection ???{ ???????public static readonly List<IEquality> Equalities = new List<IEquality> { ???????????new StructEquality(), ???????????new ValueTypeEquality(), ???????????new ArrayEquality(), ???????????new GenericCollectionEquality(), ???????????new ClassEquality() ???????}; ???}这里我们定义了一个静态类，来存储程序中使用的所有判断器。
这里在判断器集合中，实现类的其实是有顺序的，
StructEquality必须要放到ValueTypeEquality的前面，因为Struct也是值类型，如果不放到最前面，会导致判断失败。
创建判断器入口类
???public class ObjectEquality ???{ ???????public bool IsEqual(object source, object target) ???????{ ???????????if (source.GetType() != target.GetType()) ???????????{ ???????????????return false; ???????????} ???????????if (source == null && target == null) ???????????{ ???????????????return true; ???????????} ???????????else if (source == null && target != null) ???????????{ ???????????????return false; ???????????} ???????????else if (source != null && target == null) ???????????{ ???????????????return false; ???????????} ???????????var equality = EqualityCollection.Equalities ???????????????.First(p => p.MatchCondition(source)); ???????????return equality.IsEqual(source, target); ???????} ???}前面所有实现类的访问级别都是Internal, 所以我们需要创建一个判断器入口类, 外部只能通过ObjectEquality类的实例来实现判断相等。
最终效果
下面我列举几个测试用例，看看效果是不是我们想要的
对比Struct
???public struct DemoStruct ???{ ???????public int Id { get; set; } ???????public string Name { get; set; } ???} ???var a = new DemoStruct(); ???a.Id = 1; ???a.Name = "Test"; ???var b = new DemoStruct(); ???b.Id = 1; ???b.Name = "Test"; ???????var c = new DemoStruct(); ???b.Id = 2; ???b.Name = "Test"; ???????ObjectEquality objectEquality = new ObjectEquality(); ???objectEquality.IsEqual(a,b); //true ???objectEquality.IsEqual(a,c); //false对比类
???public class SimpleClass ???{ ???????public int Id { get; set; } ???????public string Name { get; set; } ???} ???var a = new SimpleClass ???{ ???????Id = 1, ???????Name = "A" ???}; ???var b = new SimpleClass ???{ ???????Id = 1, ???????Name = "A" ???}; ???????var c = new SimpleClass ???{ ???????Id = 2, ???????Name = "A" ???}; ???????ObjectEquality objectEquality = new ObjectEquality(); ???objectEquality.IsEqual(a,b); //true ???objectEquality.IsEqual(a,c); //false对比数组
???var a = new int[] { 1, 2, 3 }; ???var b = new int[] { 1, 2, 3 }; ???var c = new int[] { 1, 1, 2 }; ????????ObjectEquality objectEquality = new ObjectEquality(); ???objectEquality.IsEqual(a,b); //true ???objectEquality.IsEqual(a,c); //false.NET中如何深度判断2个对象相等
原文地址：https://www.cnblogs.com/lwqlun/p/10159770.html