C#使用表达式树实现对象复制

需求背景：对象复制性能优化；同时，在对象复制时，应跳过引用类型的null值复制，值类型支持值类型向可空类型的复制

复制代码
 1 using Common;
 2 using System;
 3 
 4 class Program
 5 {
 6     static void Main(string[] args)
 7     {
 8         TestClassA classA = new TestClassA() { PropA = new TestClass() { Name = "cs1" }, PropB = "c1", PropC = 1 };
 9         TestClassA classB = new TestClassA() { PropA = new TestClass() { Name = "cs2" }, PropB = "c2", PropC = 2 };
10         FastCopy.Copy(classA, classB, false);
11         Console.WriteLine(classB.PropA?.Name + ":" + classB.PropB + ":" + classB.PropC);
12 
13         TestClassA classC = new TestClassA() { PropA = new TestClass() { Name = "cs1" } };
14         TestClassA classD = new TestClassA() { PropA = new TestClass() { Name = "cs2" }, PropB = "c2", PropC = 2 };
15         FastCopy.Copy(classC, classD, false);
16         Console.WriteLine(classD.PropA?.Name + ":" + classD.PropB + ":" + classD.PropC);
17     }
18 }
19 public class TestClassA
20 {
21     public TestClass PropA { get; set; }
22     public string PropB { get; set; }
23     public int? PropC { get; set; }
24 }
25 public class TestClass
26 {
27     public string Name { get; set; }
28 }
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输出：

百万次调用耗时：270-300ms

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  1 using System;
  2 using System.Collections.Concurrent;
  3 using System.Collections.Generic;
  4 using System.Linq;
  5 using System.Linq.Expressions;
  6 using System.Reflection;
  7 using static System.Linq.Expressions.Expression;
  8 
  9 namespace Common
 10 {
 11     public static class FastCopy
 12     {
 13         static ConcurrentDictionary<string, object> copiers = new ConcurrentDictionary<string, object>();
 14 
 15         /// <summary>
 16         /// 复制两个对象同名属性值
 17         /// </summary>
 18         /// <typeparam name="S"></typeparam>
 19         /// <typeparam name="T"></typeparam>
 20         /// <param name="source">源对象</param>
 21         /// <param name="target">目标对象</param>
 22         /// <param name="copyNull">源对象属性值为null时，是否将值复制给目标对象</param>
 23         public static void Copy<S, T>(S source, T target, bool copyNull = true)
 24         {
 25             string name = string.Format("{0}_{1}_{2}", typeof(S), typeof(T), copyNull);
 26 
 27             object targetCopier;
 28             if (!copiers.TryGetValue(name, out targetCopier))
 29             {
 30                 Action<S, T> copier = CreateCopier<S, T>(copyNull);
 31                 copiers.TryAdd(name, copier);
 32                 targetCopier = copier;
 33             }
 34 
 35             Action<S, T> action = (Action<S, T>)targetCopier;
 36             action(source, target);
 37         }
 38 
 39         /// <summary>
 40         /// 为指定的两种类型编译生成属性复制委托
 41         /// </summary>
 42         /// <typeparam name="S"></typeparam>
 43         /// <typeparam name="T"></typeparam>
 44         /// <param name="copyNull">源对象属性值为null时，是否将值复制给目标对象</param>
 45         /// <returns></returns>
 46         private static Action<S, T> CreateCopier<S, T>(bool copyNull)
 47         {
 48             ParameterExpression source = Parameter(typeof(S));
 49             ParameterExpression target = Parameter(typeof(T));
 50             var sourceProps = typeof(S).GetProperties(BindingFlags.Instance | BindingFlags.Public).Where(p => p.CanRead).ToList();
 51             var targetProps = typeof(T).GetProperties(BindingFlags.Instance | BindingFlags.Public).Where(p => p.CanWrite).ToList();
 52 
 53             // 查找可进行赋值的属性
 54             var copyProps = targetProps.Where(tProp => sourceProps.Where(sProp => sProp.Name == tProp.Name// 名称一致 且
 55             && (
 56             sProp.PropertyType == tProp.PropertyType// 属性类型一致 或
 57             || sProp.PropertyType.IsAssignableFrom(tProp.PropertyType) // 源属性类型 为 目标属性类型 的 子类；eg：object target = string source;   或
 58             || (tProp.PropertyType.IsValueType && sProp.PropertyType.IsValueType && // 属性为值类型且基础类型一致，但目标属性为可空类型 eg：int? num = int num;
 59             ((tProp.PropertyType.GenericTypeArguments.Length > 0 ? tProp.PropertyType.GenericTypeArguments[0] : tProp.PropertyType) == sProp.PropertyType))
 60             )).Count() > 0);
 61 
 62             List<Expression> expressionList = new List<Expression>();
 63             foreach (var prop in copyProps)
 64             {
 65                 if (prop.PropertyType.IsValueType)// 属性为值类型
 66                 {
 67                     PropertyInfo sProp = typeof(S).GetProperty(prop.Name);
 68                     PropertyInfo tProp = typeof(T).GetProperty(prop.Name);
 69                     if (sProp.PropertyType == tProp.PropertyType)// 属性类型一致 eg：int num = int num;    或   int? num = int? num;
 70                     {
 71                         var assign = Assign(Property(target, prop.Name), Property(source, prop.Name));
 72                         expressionList.Add(assign);
 73                     }
 74                     else if (sProp.PropertyType.GenericTypeArguments.Length <= 0 && tProp.PropertyType.GenericTypeArguments.Length > 0)// 属性类型不一致且目标属性类型为可空类型 eg：int? num = int num;
 75                     {
 76                         var convert = Convert(Expression.Property(source, prop.Name), tProp.PropertyType);
 77                         var cvAssign = Assign(Expression.Property(target, prop.Name), convert);
 78                         expressionList.Add(cvAssign);
 79                     }
 80                 }
 81                 else// 属性为引用类型
 82                 {
 83                     var assign = Assign(Property(target, prop.Name), Property(source, prop.Name));// 编译生成属性赋值语句   target.{PropertyName} = source.{PropertyName};
 84                     var sourcePropIsNull = Equal(Constant(null, prop.PropertyType), Property(source, prop.Name));// 判断源属性值是否为Null；编译生成  source.{PropertyName} == null
 85                     var setNull = IsTrue(Constant(copyNull));// 判断是否复制Null值 编译生成  copyNull == True
 86                     var setNullTest = IfThen(setNull, assign);
 87                     var condition = IfThenElse(sourcePropIsNull, setNullTest, assign);
 88 
 89                     /**
 90                      * 编译生成
 91                      * if(source.{PropertyName} == null)
 92                      * {
 93                      *   if(setNull)
 94                      *   {
 95                      *     target.{PropertyName} = source.{PropertyName};
 96                      *   }
 97                      * }
 98                      * else
 99                      * {
100                      *   target.{PropertyName} = source.{PropertyName};
101                      * }
102                      */
103                     expressionList.Add(condition);
104                 }
105             }
106             var block = Block(expressionList.ToArray());
107             Expression<Action<S, T>> lambda = Lambda<Action<S, T>>(block, source, target);
108             return lambda.Compile();
109         }
110     }
111 }
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如果完整复制，去掉逻辑判断，同时可通过泛型类，不在使用字典，性能还可以提升。

复制代码
 1 using System;
 2 using System.Linq;
 3 using System.Linq.Expressions;
 4 using System.Reflection;
 5 
 6 namespace Common
 7 {
 8     public static class FastCopy<S, T>
 9     {
10         static Action<S, T> action = CreateCopier();
11         /// <summary>
12         /// 复制两个对象同名属性值
13         /// </summary>
14         /// <typeparam name="S"></typeparam>
15         /// <typeparam name="T"></typeparam>
16         /// <param name="source">源对象</param>
17         /// <param name="target">目标对象</param>
18         /// <param name="copyNull">源对象属性值为null时，是否将值复制给目标对象</param>
19         public static void Copy(S source, T target, bool copyNull = true)
20         {
21             action(source, target);
22         }
23 
24         /// <summary>
25         /// 为指定的两种类型编译生成属性复制委托
26         /// </summary>
27         /// <typeparam name="S"></typeparam>
28         /// <typeparam name="T"></typeparam>
29         /// <param name="copyNull">源对象属性值为null时，是否将值复制给目标对象</param>
30         /// <returns></returns>
31         private static Action<S, T> CreateCopier()
32         {
33             ParameterExpression source = Expression.Parameter(typeof(S));
34             ParameterExpression target = Expression.Parameter(typeof(T));
35             var sourceProps = typeof(S).GetProperties(BindingFlags.Instance | BindingFlags.Public).Where(p => p.CanRead).ToList();
36             var targetProps = typeof(T).GetProperties(BindingFlags.Instance | BindingFlags.Public).Where(p => p.CanWrite).ToList();
37 
38             // 查找可进行赋值的属性
39             var copyProps = targetProps.Where(tProp => sourceProps.Where(sProp => sProp.Name == tProp.Name// 名称一致 且
40             && (
41             sProp.PropertyType == tProp.PropertyType// 属性类型一致
42             )).Count() > 0);
43 
44             var block = Expression.Block(from p in copyProps select Expression.Assign(Expression.Property(target, p.Name), Expression.Property(source, p.Name)));
45             Expression<Action<S, T>> lambda = Expression.Lambda<Action<S, T>>(block, source, target);
46             return lambda.Compile();
47         }
48     }
49 }
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百万次耗时：100ms左右

出处：https://www.cnblogs.com/cs569/p/15761391.html

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原文地址：https://www.cnblogs.com/mq0036/p/15762333.html