关于比较对象，在"06判等对象是否相等"中大致可以总结为：
关于比较方法：
● 实例方法Equals(object obj)既可以比较值类型，也可以比较引用类型
● 静态方法Equals(object objA, object objB)，比较值类型
● 静态方法ReferenceEquals(object objA, object objB)，比较引用类型
● 比较引用类型可以用==，比较值类型不能用==
关于比较原则：
● 值类型比较的是值
● 引用类型比较的是引用地址
对于复杂类型，无论是复杂值类型(比如结构)还是复杂引用类型(包含值类型成员),经常要重写System.Object中的虚方法Equals(object obj)。比如，针对复杂值类型，可能这样重写：
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;
}
而现在，在NuGet上输入"Compare .NET objects",可以获取到该组件，对任何.NET对象进行比较、列出各个属性的值甚至自定义比较规则。
比较复杂类型：包含值类型成员
public class Teacher
{
public int Id { get; set; }
public string Name { get; set; }
public DateTime JoinTime { get; set; }
public TeacherClass TeacherClass { get; set; }
}
public enum TeacherClass
{
[Description("执教5年以上")]
FirstClass = 0,
[Description("执教3年以上")]
SecondClass,
[Description("执教1年以上")]
ThirdClass
}
主程序：
Teacher teacher1 = new Teacher(){Id=1,JoinTime = new DateTime(,1,1),Name = "张老师",TeacherClass = TeacherClass.FirstClass};
Teacher teacher2 = new Teacher() { Id = 2, JoinTime = new DateTime(, 1, 2), Name = "李老师", TeacherClass = TeacherClass.SecondClass };
//获取Teacher属性的个数
int propertyCount = typeof (Teacher).GetProperties().Length;
//创建比较规则
CompareLogic compareLogic = new CompareLogic()
{
Config = new ComparisonConfig()
{
MaxDifferences = propertyCount//MaxDifferences的默认值是1
}
};
bool result = pare(teacher1, teacher2).AreEqual;
Console.Write(result);
Console.ReadKey();
结果：false
比较复杂类型，并列出2个比较对象所有属性的值
Teacher teacher1 = new Teacher(){Id=1,JoinTime = new DateTime(,1,1),Name = "张老师",TeacherClass = TeacherClass.FirstClass};
Teacher teacher2 = new Teacher() { Id = 2, JoinTime = new DateTime(, 1, 2), Name = "李老师", TeacherClass = TeacherClass.SecondClass };
//获取Teacher属性的个数
int propertyCount = typeof (Teacher).GetProperties().Length;
//创建比较规则
CompareLogic compareLogic = new CompareLogic()
{
Config = new ComparisonConfig()
{
MaxDifferences = propertyCount//MaxDifferences的默认值是1
}
};
//获取2个比较对象的不同之处
List<Difference> differences = pare(teacher1, teacher2).Differences;
StringBuilder sb = new StringBuilder();
foreach (Difference diff in differences)
{
sb.AppendLine("属性名称：" + diff.PropertyName);
sb.AppendLine("第一个对象值：" + diff.Object1Value);
sb.AppendLine("第二个对象值：" + diff.Object2Value + "\r\n");
}
using (StreamWriter outfile = new StreamWriter(@"F:\CompareObjects.txt"))
{
outfile.Write(sb.ToString());
}
}
结果：
比较复杂类型，并列出2个比较对象所有属性的值，对枚举属性自定义比较规则
需要一个自定义类，继承"Compare .NET objects"的BaseTypeComparer类，把打在枚举成员上的描述特性信息输出。
重写方法IsTypeMatch()用于判断2个比较对象的属性是否是枚举，如果是枚举，就采用重写方法CompareType()所定义的关于枚举属性的比较规则。
public class CustomEnumComparer : BaseTypeComparer
{
public CustomEnumComparer() : base(RootComparerFactory.GetRootComparer()){}
public override void CompareType(ComparisonResult result, object object1, object object2, string breadCrumb)
{
if (object1.ToString() != object2.ToString())
{
Difference difference = new Difference()
{
PropertyName = breadCrumb,
Object1Value = EnumHelper.GetDescription(object1),
Object2Value = EnumHelper.GetDescription(object2),
Object1 = new WeakReference(object1), //弱对象引用，即使被引用也可被垃圾回收
Object2 = new WeakReference(object2)
};
AddDifference(result,difference);
}
}
public override bool IsTypeMatch(Type type1, Type type2)
{
return TypeHelper.IsEnum(type1) && TypeHelper.IsEnum(type2);
}
}
//获取枚举类型的描述特性
public static class EnumHelper
{
public static string GetDescription(object enumMember)
{
//获取枚举类型的字段信息
FieldInfo fi = enumMember.GetType().GetField(enumMember.ToString());
//获取字段上的描述特性
IEnumerable<DescriptionAttribute> attributes = fi.GetCustomAttributes<DescriptionAttribute>(false);
return attributes.Any() ? attributes.ElementAt(0).Description : enumMember.ToString();
}
}
只需要把针对枚举属性的自定义类赋值给CompareLogic实例即可：
Teacher teacher1 = new Teacher(){Id=1,JoinTime = new DateTime(,1,1),Name = "张老师",TeacherClass = TeacherClass.FirstClass};
Teacher teacher2 = new Teacher() { Id = 2, JoinTime = new DateTime(, 1, 2), Name = "李老师", TeacherClass = TeacherClass.SecondClass };
//获取Teacher属性的个数
int propertyCount = typeof (Teacher).GetProperties().Length;
//创建比较规则
CompareLogic compareLogic = new CompareLogic()
{
Config = new ComparisonConfig()
{
MaxDifferences = propertyCount,//MaxDifferences的默认值是1
CustomComparers = new List<BaseTypeComparer>(){new CustomEnumComparer()}
}
};
//bool result = pare(teacher1, teacher2).AreEqual;
//Console.Write(result);
//Console.ReadKey();
//获取2个比较对象的不同之处
List<Difference> differences = pare(teacher1, teacher2).Differences;
StringBuilder sb = new StringBuilder();
foreach (Difference diff in differences)
{
sb.AppendLine("属性名称：" + diff.PropertyName);
sb.AppendLine("第一个对象值：" + diff.Object1Value);
sb.AppendLine("第二个对象值：" + diff.Object2Value + "\r\n");
}
using (StreamWriter outfile = new StreamWriter(@"F:\CompareObjects.txt"))
{
outfile.Write(sb.ToString());
}
结果：
参考资料：
Compare .NET Objects Tutorial
