比较2个对象并检索具有不同值的字段列表

Question

给定一个具有35个字段的类和2个具有一定数量的不同字段值的对象.是否有一种聪明的方法来获取列表<String>以及对象如下所示的字段名称？

例如

obj1.Name = "aaa";
obj1.LastName = "bbb";
obj1.Address = "xcs";
obj2.Name = "aaa";
obj2.LastName = "ccc";
obj2.Address = "jk";

目的:

list<<String>String> containing 2 Strings LastName and Address

我认为反射是要走的路,但是35场,恐怕太重了.还有其他想法,比如linq？

Answer 1

好; 这是疯狂付出更多的努力,比我通常会去,但是这可能是一个有用的工具方法.它动态创建IL(缓存)来完成工作,处理值类型vs ref类型对象,内置IL等式,相等运算符(==),以及EqualityComparer<T>其余的:

using System.Collections.Generic;
using System.Reflection;
using System.Reflection.Emit;

namespace ConsoleApplication2
{
    using System;
    class Program
    {
        static void Main()
        {
            WriteDeltas(new Foo {X = 123, Y = DateTime.Today, Z = null},
                        new Foo {X = 124, Y = DateTime.Today, Z = null});
            WriteDeltas(new Foo { X = 123, Y = DateTime.Today, Z = null },
                        new Foo { X = 123, Y = DateTime.Now, Z = new Dummy()});
            WriteDeltas(new Bar { X = 123, Y = DateTime.Today, Z = null },
                        new Bar { X = 124, Y = DateTime.Today, Z = null });
            WriteDeltas(new Bar { X = 123, Y = DateTime.Today, Z = null },
                        new Bar { X = 123, Y = DateTime.Now, Z = new Dummy() });
        }
        static void WriteDeltas<T>(T x, T y)
        {
            Console.WriteLine("----");
            foreach(string delta in PropertyComparer<T>.GetDeltas(x,y))
            {
                Console.WriteLine(delta);
            }

        }

    }
    class Dummy {}
    class Foo
    {
        public int X { get; set; }
        public DateTime Y { get; set; }
        public Dummy Z { get; set; }
    }
    struct Bar
    {
        public int X { get; set; }
        public DateTime Y { get; set; }
        public Dummy Z { get; set; }
    }

    public static class PropertyComparer<T>
    {
        private static readonly Func<T, T, List<string>> getDeltas;
        static PropertyComparer()
        {
            var dyn = new DynamicMethod(":getDeltas", typeof (List<string>), new[] {typeof (T), typeof (T)},typeof(T));
            var il = dyn.GetILGenerator();
            il.Emit(OpCodes.Newobj, typeof (List<string>).GetConstructor(Type.EmptyTypes));
            bool isValueType = typeof (T).IsValueType;
            OpCode callType = isValueType ? OpCodes.Call : OpCodes.Callvirt;
            var add = typeof(List<string>).GetMethod("Add");
            foreach (var prop in typeof(T).GetProperties())
            {
                if (!prop.CanRead) continue;
                Label next = il.DefineLabel();
                switch (Type.GetTypeCode(prop.PropertyType))
                {
                    case TypeCode.Boolean:
                    case TypeCode.Byte:
                    case TypeCode.Char:
                    case TypeCode.Double:
                    case TypeCode.Int16:
                    case TypeCode.Int32:
                    case TypeCode.Int64:
                    case TypeCode.SByte:
                    case TypeCode.Single:
                    case TypeCode.UInt16:
                    case TypeCode.UInt32:
                    case TypeCode.UInt64:
                        if(isValueType) {il.Emit(OpCodes.Ldarga_S, (byte)0);} else {il.Emit(OpCodes.Ldarg_0);}
                        il.EmitCall(callType, prop.GetGetMethod(), null);
                        if (isValueType) { il.Emit(OpCodes.Ldarga_S, (byte)1); } else { il.Emit(OpCodes.Ldarg_1); }
                        il.EmitCall(callType, prop.GetGetMethod(), null);
                        il.Emit(OpCodes.Ceq);
                        break;
                    default:
                        var pp = new Type[] {prop.PropertyType, prop.PropertyType};
                        var eq = prop.PropertyType.GetMethod("op_Equality", BindingFlags.Public | BindingFlags.Static, null, pp, null);
                        if (eq != null)
                        {
                            if (isValueType) { il.Emit(OpCodes.Ldarga_S, (byte)0); } else { il.Emit(OpCodes.Ldarg_0); }
                            il.EmitCall(callType, prop.GetGetMethod(), null);
                            if (isValueType) { il.Emit(OpCodes.Ldarga_S, (byte)1); } else { il.Emit(OpCodes.Ldarg_1); }
                            il.EmitCall(callType, prop.GetGetMethod(), null);
                            il.EmitCall(OpCodes.Call, eq, null);

                        }
                        else
                        {
                            il.EmitCall(OpCodes.Call, typeof(EqualityComparer<>).MakeGenericType(prop.PropertyType).GetProperty("Default").GetGetMethod(), null);
                            if (isValueType) { il.Emit(OpCodes.Ldarga_S, (byte)0); } else { il.Emit(OpCodes.Ldarg_0); }
                            il.EmitCall(callType, prop.GetGetMethod(), null);
                            if (isValueType) { il.Emit(OpCodes.Ldarga_S, (byte)1); } else { il.Emit(OpCodes.Ldarg_1); }
                            il.EmitCall(callType, prop.GetGetMethod(), null);
                            il.EmitCall(OpCodes.Callvirt, typeof(EqualityComparer<>).MakeGenericType(prop.PropertyType).GetMethod("Equals", pp), null);
                        }
                        break;
                }
                il.Emit(OpCodes.Brtrue_S, next); // equal
                il.Emit(OpCodes.Dup);
                il.Emit(OpCodes.Ldstr, prop.Name);
                il.EmitCall(OpCodes.Callvirt, add, null);
                il.MarkLabel(next);
            }
            il.Emit(OpCodes.Ret);
            getDeltas = (Func<T, T, List<string>>)dyn.CreateDelegate(typeof (Func<T, T, List<string>>));
        }
        public static List<string> GetDeltas(T x, T y) { return getDeltas(x, y); }

    }
}

Answer 2

反射是解决这个问题的方法，我认为 35 个字段不是问题。

（在让自己完全困惑之后，我回想起我理解这个问题并且反思对此会很好）。