.net core 高性能对象转换

关于对象转换已经有不少轮子(AutoMapper,TinyMapper) .出于项目需要，手动造一个简单轮子。先贴代码

g>1.采用静态泛型类缓存，避免了拆箱装箱操作。

2.对于转换对象中有，字段名一样但是类型不一样的类时仍可以用

 1     public static class Mapper<TSource, TTarget> where TSource : class where TTarget : class
 2     {
 3         public readonly static Func<TSource, TTarget> Map;
 4 
 5         static Mapper()
 6         {
 7             if (Map == null)
 8                 Map = GetMap();
 9         }
10 
11         private static Func<TSource, TTarget> GetMap()
12         {
13             var sourceType = typeof(TSource);
14             var targetType = typeof(TTarget);
15 
16             var parameterExpression = Expression.Parameter(sourceType, "p");
17             var memberInitExpression = GetExpression(parameterExpression, sourceType, targetType);
18 
19             var lambda = Expression.Lambda<Func<TSource, TTarget>>(memberInitExpression, parameterExpression);
20             return lambda.Compile();
21         }
22 
23         /// <summary>
24         /// 根据转换源和目标获取表达式树
25         /// </summary>
26         /// <param name="parameterExpression">表达式参数p</param>
27         /// <param name="sourceType">转换源类型</param>
28         /// <param name="targetType">转换目标类型</param>
29         /// <returns></returns>
30         private static MemberInitExpression GetExpression(Expression parameterExpression, Type sourceType, Type targetType)
31         {
32             var memberBindings = new List<MemberBinding>();
33             foreach (var targetItem in targetType.GetProperties().Where(x => x.PropertyType.IsPublic && x.CanWrite))
34             {
35                 var sourceItem = sourceType.GetProperty(targetItem.Name);
36 
37                 //判断实体的读写权限
38                 if (sourceItem == null || !sourceItem.CanRead || sourceItem.PropertyType.IsNotPublic)
39                     continue;
40 
41                 //标注NotMapped特性的属性忽略转换
42                 if (sourceItem.GetCustomAttribute<NotMappedAttribute>() != null)
43                     continue;
44 
45                 var propertyExpression = Expression.Property(parameterExpression, sourceItem);
46 
47                 //判断都是class 且类型不相同时
48                 if (targetItem.PropertyType.IsClass && sourceItem.PropertyType.IsClass && targetItem.PropertyType != sourceItem.PropertyType)
49                 {
50                     if (targetItem.PropertyType != targetType)//防止出现自己引用自己无限递归
51                     {
52                         var memberInit = GetExpression(propertyExpression, sourceItem.PropertyType, targetItem.PropertyType);
53                         memberBindings.Add(Expression.Bind(targetItem, memberInit));
54                         continue;
55                     }
56                 }
57 
58                 if (targetItem.PropertyType != sourceItem.PropertyType)
59                     continue;
60 
61                 memberBindings.Add(Expression.Bind(targetItem, propertyExpression));
62             }
63             return Expression.MemberInit(Expression.New(targetType), memberBindings);
64         }
65     }

View Code

3.调用方法如下

（1）构造样例类

    public class A
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public C User { get; set; }

        /// <summary>
        /// 标注为notmapped特性时，不转换赋值
        /// </summary>
        [System.ComponentModel.DataAnnotations.Schema.NotMapped]
        public D UserA { get; set; }

    }

    public class B
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public D User { get; set; }

        public D UserA { get; set; }
    }

    public class C
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

    public class D
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

(2) 调用

            var a = new A
            {
                Id = 1,
                Name = "张三",
                User = new C
                {
                    Id = 1,
                    Name = "李四"
                }
            };

            B b = Mapper<A, B>.Map(a);//得到转换结果

4.性能测试

           var length = 10000000;
            var listA = new List<A>();
            for (int i = 0; i < length; i++)
            {
                listA.Add(new A
                {
                    Id = i,
                    Name = "张三",
                    User = new C
                    {
                        Id = i,
                        Name = "李四"
                    }
                });
            }

            var sw = Stopwatch.StartNew();
            for (int i = 0; i < length; i++)
            {
                var item = listA[i];
                var b = new B
                {
                    Id = item.Id,
                    Name = item.Name,
                    User = new D
                    {
                        Id = i,
                        Name = "李四",
                    }
                };
            }
            sw.Stop();
            Console.WriteLine($"原生的时间:{sw.ElapsedMilliseconds}ms");

            //表达式
            Mapper<A, B>.Map(listA[0]);//预先编译缓存
            sw.Restart();
            for (int i = 0; i < length; i++)
            {
                Mapper<A, B>.Map(listA[i]);
            }
            sw.Stop();
            Console.WriteLine($"表达式的时间:{sw.ElapsedMilliseconds}ms");

            Console.ReadLine();

5. 1000万数据不带子类集结果