实体类编程的最佳伴侣——高效的实体类复制
在面向对象编程的时代，实体类的操作已经越来越普遍了，从数据库中获取数据，离线存储在实体类集合中，对集合的修改再反馈到数据库中等。对于实体类的修改就意味着对数据库的修改，为了更好的自动化编程，减少编码量，同时也为了提高运行速度，这里发布个代码类——对象的深度拷贝和对象属性的浅拷贝， 利用了Emit操作，执行速度肯定是最快的。
ObjectCopy
public static class ObjectCopy { struct Identity { int _hashcode; RuntimeTypeHandle _type; public Identity(int hashcode, RuntimeTypeHandle type) { _hashcode = hashcode; _type = type; } } //缓存对象复制的方法。 static Dictionary<Type, Func<object, Dictionary<Identity, object>, object>> methods1 = new Dictionary<Type, Func<object, Dictionary<Identity, object>, object>>(); static Dictionary<Type, Action<object, Dictionary<Identity, object>, object>> methods2 = new Dictionary<Type, Action<object, Dictionary<Identity, object>, object>>(); static Dictionary<Type, Action<object, Dictionary<Identity, object>, object>> methods3 = new Dictionary<Type, Action<object, Dictionary<Identity, object>, object>>(); static List<FieldInfo> GetSettableFields(Type t) { return t.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance).ToList(); } class PropInfo { public string Name { get; set; } public MethodInfo Getter { get; set; } public MethodInfo Setter { get; set; } public Type Type { get; set; } } static List<PropInfo> GetPublicProps(Type t) { return t .GetProperties() .Select(p => new PropInfo { Name = p.Name, Getter = p.DeclaringType == t ? p.GetGetMethod(true) : p.DeclaringType.GetProperty(p.Name).GetGetMethod(true), Setter = p.DeclaringType == t ? p.GetSetMethod(true) : p.DeclaringType.GetProperty(p.Name).GetSetMethod(true), Type = p.PropertyType }) .Where(info => info.Getter != null && info.Setter != null) .ToList(); } static Func<object, Dictionary<Identity, object>, object> CreateCloneMethod1(Type type, Dictionary<Identity, object> objects) { Type tmptype; var fields = GetSettableFields(type); var dm = new DynamicMethod(string.Format("Clone{0}", Guid.NewGuid()), typeof(object), new[] { typeof(object), typeof(Dictionary<Identity, object>) }, true); var il = dm.GetILGenerator(); il.DeclareLocal(type); il.DeclareLocal(type); il.DeclareLocal(typeof(Identity)); if (!type.IsArray) { il.Emit(OpCodes.Newobj, type.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null)); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Stloc_1); il.Emit(OpCodes.Ldloca_S, 2); il.Emit(OpCodes.Ldarg_0); il.Emit(OpCodes.Castclass, type); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Stloc_0); il.Emit(OpCodes.Callvirt, typeof(object).GetMethod("GetHashCode")); il.Emit(OpCodes.Ldtoken, type); il.Emit(OpCodes.Call, typeof(Identity).GetConstructor(BindingFlags.Instance | BindingFlags.Public, null, new[] { typeof(int), typeof(RuntimeTypeHandle) }, null)); il.Emit(OpCodes.Ldarg_1); il.Emit(OpCodes.Ldloc_2); il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Callvirt, typeof(Dictionary<Identity, object>).GetMethod("Add")); foreach (var field in fields) { if (!field.FieldType.IsValueType && field.FieldType != typeof(String)) { //不符合条件的字段，直接忽略，避免报错。 if ((field.FieldType.IsArray && (field.FieldType.GetArrayRank() > 1 || (!(tmptype = field.FieldType.GetElementType()).IsValueType && tmptype != typeof(String) && tmptype.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null) == null))) || (!field.FieldType.IsArray && field.FieldType.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null) == null)) break; il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldfld, field); il.Emit(OpCodes.Ldarg_1); il.EmitCall(OpCodes.Call, typeof(ObjectCopy).GetMethod("CopyImpl1", BindingFlags.NonPublic | BindingFlags.Static).MakeGenericMethod(field.FieldType), null); il.Emit(OpCodes.Stfld, field); } else { il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldfld, field); il.Emit(OpCodes.Stfld, field); } } for (type = type.BaseType; type != null && type != typeof(object); type = type.BaseType) { //只需要查找基类的私有成员，共有或受保护的在派生类中直接被复制过了。 fields = type.GetFields(BindingFlags.NonPublic | BindingFlags.Instance).ToList(); foreach (var field in fields) { if (!field.FieldType.IsValueType && field.FieldType != typeof(String)) { //不符合条件的字段，直接忽略，避免报错。 if ((field.FieldType.IsArray && (field.FieldType.GetArrayRank() > 1 || (!(tmptype = field.FieldType.GetElementType()).IsValueType && tmptype != typeof(String) && tmptype.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null) == null))) || (!field.FieldType.IsArray && field.FieldType.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null) == null)) break; il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldfld, field); il.Emit(OpCodes.Ldarg_1); il.EmitCall(OpCodes.Call, typeof(ObjectCopy).GetMethod("CopyImpl1", BindingFlags.NonPublic | BindingFlags.Static).MakeGenericMethod(field.FieldType), null); il.Emit(OpCodes.Stfld, field); } else { il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldfld, field); il.Emit(OpCodes.Stfld, field); } } } } else { Type arraytype = type.GetElementType(); var i = il.DeclareLocal(typeof(int)); var lb1 = il.DefineLabel(); var lb2 = il.DefineLabel(); il.Emit(OpCodes.Ldarg_0); il.Emit(OpCodes.Castclass, type); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Stloc_0); il.Emit(OpCodes.Ldlen); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Ldc_I4_1); il.Emit(OpCodes.Sub); il.Emit(OpCodes.Stloc, i); il.Emit(OpCodes.Newarr, arraytype); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Stloc_1); il.Emit(OpCodes.Ldloca_S, 2); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Callvirt, typeof(object).GetMethod("GetHashCode")); il.Emit(OpCodes.Ldtoken, type); il.Emit(OpCodes.Call, typeof(Identity).GetConstructor(BindingFlags.Instance | BindingFlags.Public, null, new[] { typeof(int), typeof(RuntimeTypeHandle) }, null)); il.Emit(OpCodes.Ldarg_1); il.Emit(OpCodes.Ldloc_2); il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Callvirt, typeof(Dictionary<Identity, object>).GetMethod("Add")); il.Emit(OpCodes.Ldloc, i); il.Emit(OpCodes.Br, lb1); il.MarkLabel(lb2); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Ldloc, i); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldloc, i); il.Emit(OpCodes.Ldelem, arraytype); if (!arraytype.IsValueType && arraytype != typeof(String)) { il.EmitCall(OpCodes.Call, typeof(ObjectCopy).GetMethod("CopyImpl1", BindingFlags.NonPublic | BindingFlags.Static).MakeGenericMethod(arraytype), null); } il.Emit(OpCodes.Stelem, arraytype); il.Emit(OpCodes.Ldloc, i); il.Emit(OpCodes.Ldc_I4_1); il.Emit(OpCodes.Sub); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Stloc, i); il.MarkLabel(lb1); il.Emit(OpCodes.Ldc_I4_0); il.Emit(OpCodes.Clt); il.Emit(OpCodes.Brfalse, lb2); } il.Emit(OpCodes.Ret); return (Func<object, Dictionary<Identity, object>, object>)dm.CreateDelegate(typeof(Func<object, Dictionary<Identity, object>, object>)); } static Action<object, Dictionary<Identity, object>, object> CreateCloneMethod2(Type type, Dictionary<Identity, object> objects) { Type tmptype; var fields = GetSettableFields(type); var dm = new DynamicMethod(string.Format("Copy{0}", Guid.NewGuid()), null, new[] { typeof(object), typeof(Dictionary<Identity, object>), typeof(object) }, true); var il = dm.GetILGenerator(); il.DeclareLocal(type); il.DeclareLocal(type); il.DeclareLocal(typeof(Identity)); if (!type.IsArray) { il.Emit(OpCodes.Ldarg_2); il.Emit(OpCodes.Castclass, type); il.Emit(OpCodes.Stloc_1); il.Emit(OpCodes.Ldarg_0); il.Emit(OpCodes.Castclass, type); il.Emit(OpCodes.Stloc_0); foreach (var field in fields) { if (!field.FieldType.IsValueType && field.FieldType != typeof(String)) { //不符合条件的字段，直接忽略，避免报错。 if ((field.FieldType.IsArray && (field.FieldType.GetArrayRank() > 1 || (!(tmptype = field.FieldType.GetElementType()).IsValueType && tmptype != typeof(String) && tmptype.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null) == null))) || (!field.FieldType.IsArray && field.FieldType.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null) == null)) break; il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldfld, field); il.Emit(OpCodes.Ldarg_1); il.EmitCall(OpCodes.Call, typeof(ObjectCopy).GetMethod("CopyImpl1", BindingFlags.NonPublic | BindingFlags.Static).MakeGenericMethod(field.FieldType), null); il.Emit(OpCodes.Stfld, field); } else { il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldfld, field); il.Emit(OpCodes.Stfld, field); } } for (type = type.BaseType; type != null && type != typeof(object); type = type.BaseType) { //只需要查找基类的私有成员，共有或受保护的在派生类中直接被复制过了。 fields = type.GetFields(BindingFlags.NonPublic | BindingFlags.Instance).ToList(); foreach (var field in fields) { if (!field.FieldType.IsValueType && field.FieldType != typeof(String)) { //不符合条件的字段，直接忽略，避免报错。 if ((field.FieldType.IsArray && (field.FieldType.GetArrayRank() > 1 || (!(tmptype = field.FieldType.GetElementType()).IsValueType && tmptype != typeof(String) && tmptype.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null) == null))) || (!field.FieldType.IsArray && field.FieldType.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null) == null)) break; il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldfld, field); il.Emit(OpCodes.Ldarg_1); il.EmitCall(OpCodes.Call, typeof(ObjectCopy).GetMethod("CopyImpl1", BindingFlags.NonPublic | BindingFlags.Static).MakeGenericMethod(field.FieldType), null); il.Emit(OpCodes.Stfld, field); } else { il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldfld, field); il.Emit(OpCodes.Stfld, field); } } } } else { Type arraytype = type.GetElementType(); var i = il.DeclareLocal(typeof(int)); var lb1 = il.DefineLabel(); var lb2 = il.DefineLabel(); il.Emit(OpCodes.Ldarg_0); il.Emit(OpCodes.Castclass, type); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Stloc_0); il.Emit(OpCodes.Ldlen); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Ldc_I4_1); il.Emit(OpCodes.Sub); il.Emit(OpCodes.Stloc, i); il.Emit(OpCodes.Ldarg_2); il.Emit(OpCodes.Castclass, type); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Stloc_1); il.Emit(OpCodes.Ldloc, i); il.Emit(OpCodes.Br, lb1); il.MarkLabel(lb2); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Ldloc, i); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldloc, i); il.Emit(OpCodes.Ldelem, arraytype); if (!arraytype.IsValueType && arraytype != typeof(String)) { il.EmitCall(OpCodes.Call, typeof(ObjectCopy).GetMethod("CopyImpl1", BindingFlags.NonPublic | BindingFlags.Static).MakeGenericMethod(arraytype), null); } il.Emit(OpCodes.Stelem, arraytype); il.Emit(OpCodes.Ldloc, i); il.Emit(OpCodes.Ldc_I4_1); il.Emit(OpCodes.Sub); il.Emit(OpCodes.Dup); il.Emit(OpCodes.Stloc, i); il.MarkLabel(lb1); il.Emit(OpCodes.Ldc_I4_0); il.Emit(OpCodes.Clt); il.Emit(OpCodes.Brfalse, lb2); } il.Emit(OpCodes.Ret); return (Action<object, Dictionary<Identity, object>, object>)dm.CreateDelegate(typeof(Action<object, Dictionary<Identity, object>, object>)); } /// <summary> /// 对属性进行复制，不查找父类，用于当前实体对象的属性拷贝。 /// </summary> /// <param name="type">实体类型</param> /// <param name="objects">复制链</param> /// <returns></returns> static Action<object, Dictionary<Identity, object>, object> CreateCloneMethod3(Type type, Dictionary<Identity, object> objects) { var props = GetPublicProps(type); var dm = new DynamicMethod(string.Format("Copy{0}", Guid.NewGuid()), null, new[] { typeof(object), typeof(Dictionary<Identity, object>), typeof(object) }, true); var il = dm.GetILGenerator(); il.DeclareLocal(type);//存放源对象 il.DeclareLocal(type);//存放目标对象 il.DeclareLocal(typeof(Identity));//存放标识 if (!type.IsArray) { il.Emit(OpCodes.Ldarg_2); il.Emit(OpCodes.Castclass, type); il.Emit(OpCodes.Stloc_1);//将参数中获取的目标对象存放到局部变量1中 il.Emit(OpCodes.Ldarg_0); il.Emit(OpCodes.Castclass, type); il.Emit(OpCodes.Stloc_0);//将参数中获取的源对象存放到局部变量0中 foreach (var prop in props) { if (!prop.Type.IsValueType && prop.Type != typeof(String)) { //不符合条件的属性，直接忽略。 if (prop.Type.IsArray) break; il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Call, prop.Getter);//获取局部变量0中暂存的源对象的属性 il.Emit(OpCodes.Ldarg_1);//加载参数中的复制链对象 il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Call, prop.Getter);//获取局部变量1中暂存的目标对象的属性 il.EmitCall(OpCodes.Call, typeof(ObjectCopy).GetMethod("CopyImpl2", BindingFlags.NonPublic | BindingFlags.Static).MakeGenericMethod(prop.Type), null); } else { il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Call, prop.Getter); il.Emit(OpCodes.Call, prop.Setter); } } } il.Emit(OpCodes.Ret); return (Action<object, Dictionary<Identity, object>, object>)dm.CreateDelegate(typeof(Action<object, Dictionary<Identity, object>, object>)); } static T CopyImpl1<T>(T source, Dictionary<Identity, object> objects) where T : class { //为空则直接返回null if (source == null) return null; Type type = source.GetType(); Identity id = new Identity(source.GetHashCode(), type.TypeHandle); object result; //如果发现曾经复制过，用之前的，从而停止递归复制。 if (!objects.TryGetValue(id, out result)) { //最后查找对象的复制方法，如果不存在，创建新的。 Func<object, Dictionary<Identity, object>, object> method; if (!methods1.TryGetValue(type, out method)) { method = CreateCloneMethod1(type, objects); methods1.Add(type, method); } result = method(source, objects); } return (T)result; } static void CopyImpl2<T>(T source, T target, Dictionary<Identity, object> objects) where T : class { Type type = typeof(T); Identity id = new Identity(source.GetHashCode(), type.TypeHandle); object result; //如果发现曾经复制过，用之前的，从而停止递归复制。 if (!objects.TryGetValue(id, out result)) { objects.Add(new Identity(source.GetHashCode(), type.TypeHandle), source); //最后查找对象的复制方法，如果不存在，创建新的。 Action<object, Dictionary<Identity, object>, object> method; if (!methods3.TryGetValue(type, out method)) { method = CreateCloneMethod3(type, objects); methods3.Add(type, method); } method(source, objects, target); } } /// <summary> /// 创建对象深度复制的副本 /// </summary> public static T ToObjectCopy<T>(this T source) where T : class { Type type = source.GetType(); Dictionary<Identity, object> objects = new Dictionary<Identity, object>();//存放内嵌引用类型的复制链，避免构成一个环。 Func<object, Dictionary<Identity, object>, object> method; if (!methods1.TryGetValue(type, out method)) { method = CreateCloneMethod1(type, objects); methods1.Add(type, method); } return (T)method(source, objects); } /// <summary> /// 将source对象的所有属性复制到target对象中，深度复制 /// </summary> public static void ObjectCopyTo<T>(this T source, T target) where T : class { if (target == null) throw new Exception("将要复制的目标未初始化"); Type type = source.GetType(); if (type != target.GetType()) throw new Exception("要复制的对象类型不同，无法复制"); Dictionary<Identity, object> objects = new Dictionary<Identity, object>();//存放内嵌引用类型的复制链，避免构成一个环。 objects.Add(new Identity(source.GetHashCode(), type.TypeHandle), source); Action<object, Dictionary<Identity, object>, object> method; if (!methods2.TryGetValue(type, out method)) { method = CreateCloneMethod2(type, objects); methods2.Add(type, method); } method(source, objects, target); } /// <summary> /// 将source对象的所有属性复制到target对象中，仅对公有属性复制，不查找父类，不创建引用属性，但复制引用属性内部的属性。 /// </summary> public static void PropCopyTo<T>(this T source, T target) where T : class { if (target == null) throw new Exception("将要复制的目标未初始化"); Type type = typeof(T); Dictionary<Identity, object> objects = new Dictionary<Identity, object>();//存放内嵌引用类型的复制链，避免构成一个环。 objects.Add(new Identity(source.GetHashCode(), type.TypeHandle), source); Action<object, Dictionary<Identity, object>, object> method; if (!methods3.TryGetValue(type, out method)) { method = CreateCloneMethod3(type, objects); methods3.Add(type, method); } method(source, objects, target); } }
代码中，ToObjectCopy是为了创建一个新的实体对象，ObjectCopyTo是为了将实体对象深度复制到另一个实体对象上面，PropCopyTo则是为了将对象属性浅拷贝另一个对象中。
一、为什么要深度复制实体？
如果实体类中某个属性是byte[]类型的，一般的赋值是传递地址，显然不深度拷贝就不能完成类似引用类型属性的真正拷贝。
二、如果实体类中某个实体的属性是另一个实体类，是否会被复制？
会，因此设计实体类的时候，不要将引用关系直接设计到类的属性中，虽然可以清晰的访问父子关系，但是实体类在创建时难度就会增加，不利于自动化编程，实体就应该如实反映数据库的表结构。
三、为什么要属性的浅拷贝？
因为对象的深度拷贝是通过字段的直接赋值实现的，那样效率最高，但是跳过了属性访问器，无法触发属性变化的事件，而对于实体类集合特别是ObservableCollection<T>需要通知UI刷新，需要触发属性变化的事件，一些数据库自动更新也是通过属性改变事件来触发的。
四、什么时候要复制实体？
当我们需要一个对实体修改的临时副本，不直接对数据源操作的时候，就需要用到它，这样可以提供一个取消操作的可能——放弃被修改的实体对象即可。
曾在CSDN上发布过一个类似版本，这是改进版，都是本人原创。