26复杂类型比较,使用Compare .NET objects组件

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;

}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

 

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(2014,1,1),Name = "张老师",TeacherClass = TeacherClass.FirstClass};

            Teacher teacher2 = new Teacher() { Id = 2, JoinTime = new DateTime(2014, 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 = compareLogic.Compare(teacher1, teacher2).AreEqual;

            Console.Write(result);

            Console.ReadKey();    

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

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(2014,1,1),Name = "张老师",TeacherClass = TeacherClass.FirstClass};

            Teacher teacher2 = new Teacher() { Id = 2, JoinTime = new DateTime(2014, 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 = compareLogic.Compare(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());

            }

        }  

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

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();

        }

    }

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

 

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(2014,1,1),Name = "张老师",TeacherClass = TeacherClass.FirstClass};

            Teacher teacher2 = new Teacher() { Id = 2, JoinTime = new DateTime(2014, 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 = compareLogic.Compare(teacher1, teacher2).AreEqual;

            //Console.Write(result);

            //Console.ReadKey();

            //获取2个比较对象的不同之处

            List<Difference> differences = compareLogic.Compare(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());

            }

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

结果：

 

参考资料：

Compare .NET Objects Tutorial