反射获取 PropertyInfo 可以对对象的属性值进行读取或者写入，但是这样性能不好。所以，我们需要更快的方案。

方案说明

就是用表达式编译一个Action<TObj,TValue>作为 Setter，编译一个Func<TObj,TValue>作为 Getter。

然后把这些编译好的委托放在一个泛型类的静态字段中保存起来，需要使用的时候从这里面查找就可以了。

知识要点

1. 使用表达式创建委托

2. 泛型类的静态字段是每个闭合类型独立的，因此用于存储和类型相关的内容非常方便

实现代码

由于代码中混合的使用 Switch 作为字典的阴招，所以代码很长，此处不再罗列，仅给出链接：

• - [Github ValueGetter](https://github.com/newbe36524/Newbe.ObjectVisitor/blob/main/src/Newbe.ObjectVisitor/Newbe.ObjectVisitor/Core/ValueGetter.cs)

• - [Github ValueSetter](https://github.com/newbe36524/Newbe.ObjectVisitor/blob/main/src/Newbe.ObjectVisitor/Newbe.ObjectVisitor/Core/ValueSetter.cs)

• - [Gitee ValueGetter](https://gitee.com/yks/Newbe.ObjectVisitor/blob/main/src/Newbe.ObjectVisitor/Newbe.ObjectVisitor/Core/ValueGetter.cs)

• - [Gitee ValueSetter](https://gitee.com/yks/Newbe.ObjectVisitor/blob/main/src/Newbe.ObjectVisitor/Newbe.ObjectVisitor/Core/ValueSetter.cs)

基准测试

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19041.572 (2004/?/20H1)
Intel Xeon CPU E5-2678 v3 2.50GHz, 1 CPU, 24 logical and 12 physical cores
.NET Core SDK=5.0.100-rc.2.20479.15[Host]       : .NET Core 2.1.23 (CoreCLR 4.6.29321.03, CoreFX 4.6.29321.01), X64 RyuJITnet461       : .NET Framework 4.8 (4.8.4250.0), X64 RyuJITnet48        : .NET Framework 4.8 (4.8.4250.0), X64 RyuJITnetcoreapp21 : .NET Core 2.1.23 (CoreCLR 4.6.29321.03, CoreFX 4.6.29321.01), X64 RyuJITnetcoreapp31 : .NET Core 3.1.9 (CoreCLR 4.700.20.47201, CoreFX 4.700.20.47203), X64 RyuJITnetcoreapp5  : .NET Core 5.0.0 (CoreCLR 5.0.20.47505, CoreFX 5.0.20.47505), X64 RyuJIT

结论

1. 使用委托明显比使用 PropertyInfo 要快，这个方案可以。

2. Framework 真拉胯，Net 5 简直太强了。

3. 如果属性是明确的，建议把字典中取出来的委托保存在自己的上下文，这可以明显的省去查找的消耗。

图表

从左往右分别是：直接读取属性、缓存委托、不缓存委托和使用 PropertyInfo。

数据

Getter

Method	Job	Runtime	Mean	Error	StdDev	Median	Ratio	RatioSD	Rank
DirectlyString	net461	.NET 4.6.1	0.1636 ns	0.0822 ns	0.1126 ns	0.1472 ns	?	?	2
DirectlyInt	net461	.NET 4.6.1	0.0318 ns	0.0348 ns	0.0342 ns	0.0217 ns	?	?	1
ReflectString	net461	.NET 4.6.1	145.8375 ns	2.2790 ns	2.1317 ns	145.6522 ns	?	?	7
ReflectInt	net461	.NET 4.6.1	172.5066 ns	1.3206 ns	1.1028 ns	172.6804 ns	?	?	8
GetterString	net461	.NET 4.6.1	31.4379 ns	0.6017 ns	0.5334 ns	31.6316 ns	?	?	4
GetterInt	net461	.NET 4.6.1	33.0642 ns	0.4940 ns	0.4380 ns	33.0557 ns	?	?	5
GetterObject	net461	.NET 4.6.1	33.9174 ns	0.5587 ns	0.5226 ns	33.7326 ns	?	?	6
GetterCached	net461	.NET 4.6.1	7.5878 ns	0.1223 ns	0.1144 ns	7.5765 ns	?	?	3
DirectlyString	net48	.NET 4.8	0.0181 ns	0.0353 ns	0.0313 ns	0.0043 ns	?	?	1
DirectlyInt	net48	.NET 4.8	0.0050 ns	0.0089 ns	0.0079 ns	0.0000 ns	?	?	1
ReflectString	net48	.NET 4.8	143.8313 ns	2.2501 ns	2.1047 ns	143.5568 ns	?	?	5
ReflectInt	net48	.NET 4.8	172.1714 ns	1.9819 ns	1.7569 ns	172.3142 ns	?	?	6
GetterString	net48	.NET 4.8	31.5887 ns	0.6310 ns	0.5902 ns	31.5385 ns	?	?	3
GetterInt	net48	.NET 4.8	32.7140 ns	0.3992 ns	0.3734 ns	32.7343 ns	?	?	4
GetterObject	net48	.NET 4.8	33.3063 ns	0.2069 ns	0.1834 ns	33.3053 ns	?	?	4
GetterCached	net48	.NET 4.8	7.5540 ns	0.2201 ns	0.1951 ns	7.5069 ns	?	?	2
DirectlyString	netcoreapp21	.NET Core 2.1	0.0000 ns	0.0000 ns	0.0000 ns	0.0000 ns	?	?	1
DirectlyInt	netcoreapp21	.NET Core 2.1	0.0193 ns	0.0111 ns	0.0104 ns	0.0177 ns	?	?	2
ReflectString	netcoreapp21	.NET Core 2.1	110.4180 ns	2.2159 ns	1.8503 ns	110.8038 ns	?	?	7
ReflectInt	netcoreapp21	.NET Core 2.1	138.9612 ns	0.9694 ns	0.8594 ns	138.8217 ns	?	?	8
GetterString	netcoreapp21	.NET Core 2.1	16.8958 ns	0.2384 ns	0.2230 ns	16.8103 ns	?	?	4
GetterInt	netcoreapp21	.NET Core 2.1	19.4407 ns	0.2041 ns	0.1809 ns	19.4539 ns	?	?	6
GetterObject	netcoreapp21	.NET Core 2.1	18.6922 ns	0.2700 ns	0.2255 ns	18.6582 ns	?	?	5
GetterCached	netcoreapp21	.NET Core 2.1	0.9299 ns	0.0457 ns	0.0427 ns	0.9308 ns	?	?	3
DirectlyString	netcoreapp31	.NET Core 3.1	0.0000 ns	0.0000 ns	0.0000 ns	0.0000 ns	?	?	1
DirectlyInt	netcoreapp31	.NET Core 3.1	0.0693 ns	0.0102 ns	0.0091 ns	0.0709 ns	?	?	2
ReflectString	netcoreapp31	.NET Core 3.1	98.6735 ns	0.8335 ns	0.7389 ns	98.5319 ns	?	?	7
ReflectInt	netcoreapp31	.NET Core 3.1	130.6941 ns	0.9332 ns	0.8730 ns	130.5376 ns	?	?	8
GetterString	netcoreapp31	.NET Core 3.1	14.8915 ns	0.2025 ns	0.1795 ns	14.8911 ns	?	?	4
GetterInt	netcoreapp31	.NET Core 3.1	16.2874 ns	0.0789 ns	0.0700 ns	16.2753 ns	?	?	5
GetterObject	netcoreapp31	.NET Core 3.1	17.6202 ns	0.1130 ns	0.1057 ns	17.6092 ns	?	?	6
GetterCached	netcoreapp31	.NET Core 3.1	0.6351 ns	0.0244 ns	0.0217 ns	0.6393 ns	?	?	3
DirectlyString	netcoreapp5	.NET Core 5.0	0.5098 ns	0.0328 ns	0.0291 ns	0.5131 ns	1.000	0.00	2
DirectlyInt	netcoreapp5	.NET Core 5.0	0.0000 ns	0.0000 ns	0.0000 ns	0.0000 ns	0.000	0.00	1
ReflectString	netcoreapp5	.NET Core 5.0	88.8937 ns	0.9697 ns	0.8596 ns	88.7457 ns	174.838	9.26	7
ReflectInt	netcoreapp5	.NET Core 5.0	123.4464 ns	1.0582 ns	0.9898 ns	123.3193 ns	242.996	14.00	8
GetterString	netcoreapp5	.NET Core 5.0	7.6628 ns	0.0931 ns	0.0777 ns	7.6703 ns	15.031	0.95	5
GetterInt	netcoreapp5	.NET Core 5.0	6.6645 ns	0.0825 ns	0.0772 ns	6.6497 ns	13.085	0.69	4
GetterObject	netcoreapp5	.NET Core 5.0	8.3090 ns	0.1685 ns	0.1576 ns	8.2865 ns	16.344	0.83	6
GetterCached	netcoreapp5	.NET Core 5.0	0.9791 ns	0.0293 ns	0.0245 ns	0.9764 ns	1.920	0.13	3

Setter

Method	Job	Runtime	Mean	Error	StdDev	Median	Ratio	RatioSD	Rank
DirectlyString	net461	.NET 4.6.1	2.0161 ns	0.0300 ns	0.0266 ns	2.0045 ns	1.000	0.00	2
DirectlyInt	net461	.NET 4.6.1	0.0076 ns	0.0094 ns	0.0083 ns	0.0081 ns	0.004	0.00	1
ReflectString	net461	.NET 4.6.1	237.5006 ns	4.5706 ns	4.4890 ns	236.5912 ns	117.871	3.40	5
ReflectInt	net461	.NET 4.6.1	249.3627 ns	2.1717 ns	2.0314 ns	249.0283 ns	123.681	1.94	6
GetterString	net461	.NET 4.6.1	32.8621 ns	0.2855 ns	0.2229 ns	32.9189 ns	16.335	0.22	4
GetterInt	net461	.NET 4.6.1	33.6103 ns	0.4245 ns	0.3544 ns	33.5499 ns	16.695	0.26	4
GetterObject	net461	.NET 4.6.1	33.2561 ns	0.2966 ns	0.2629 ns	33.1795 ns	16.497	0.17	4
GetterCached	net461	.NET 4.6.1	9.1805 ns	0.0761 ns	0.0674 ns	9.1802 ns	4.554	0.08	3
DirectlyString	net48	.NET 4.8	1.9272 ns	0.0298 ns	0.0264 ns	1.9245 ns	1.000	0.00	2
DirectlyInt	net48	.NET 4.8	0.0000 ns	0.0000 ns	0.0000 ns	0.0000 ns	0.000	0.00	1
ReflectString	net48	.NET 4.8	237.7686 ns	4.6597 ns	5.3661 ns	235.8445 ns	123.908	3.57	5
ReflectInt	net48	.NET 4.8	249.6291 ns	4.5333 ns	4.2404 ns	249.5459 ns	129.689	3.13	6
GetterString	net48	.NET 4.8	32.2366 ns	0.1941 ns	0.1721 ns	32.1780 ns	16.731	0.29	4
GetterInt	net48	.NET 4.8	32.0081 ns	0.1488 ns	0.1162 ns	32.0270 ns	16.572	0.23	4
GetterObject	net48	.NET 4.8	32.6413 ns	0.1417 ns	0.1183 ns	32.6260 ns	16.907	0.24	4
GetterCached	net48	.NET 4.8	9.2589 ns	0.0928 ns	0.0868 ns	9.2564 ns	4.799	0.07	3
DirectlyString	netcoreapp21	.NET Core 2.1	2.4107 ns	0.0507 ns	0.0475 ns	2.3936 ns	1.000	0.00	2
DirectlyInt	netcoreapp21	.NET Core 2.1	0.0007 ns	0.0028 ns	0.0025 ns	0.0000 ns	0.000	0.00	1
ReflectString	netcoreapp21	.NET Core 2.1	203.6637 ns	3.6109 ns	3.3777 ns	203.4793 ns	84.517	2.31	7
ReflectInt	netcoreapp21	.NET Core 2.1	213.8619 ns	2.1882 ns	1.9398 ns	213.7367 ns	88.757	1.71	8
GetterString	netcoreapp21	.NET Core 2.1	19.5240 ns	0.0811 ns	0.0758 ns	19.5149 ns	8.102	0.15	5
GetterInt	netcoreapp21	.NET Core 2.1	18.8794 ns	0.1193 ns	0.1058 ns	18.8837 ns	7.836	0.18	4
GetterObject	netcoreapp21	.NET Core 2.1	20.6765 ns	0.2709 ns	0.2115 ns	20.6419 ns	8.584	0.14	6
GetterCached	netcoreapp21	.NET Core 2.1	2.7606 ns	0.0613 ns	0.0512 ns	2.7590 ns	1.148	0.02	3
DirectlyString	netcoreapp31	.NET Core 3.1	2.2625 ns	0.0647 ns	0.0605 ns	2.2555 ns	1.000	0.00	2
DirectlyInt	netcoreapp31	.NET Core 3.1	0.0072 ns	0.0165 ns	0.0146 ns	0.0000 ns	0.003	0.01	1
ReflectString	netcoreapp31	.NET Core 3.1	182.7306 ns	3.3249 ns	3.1101 ns	182.3062 ns	80.804	1.99	7
ReflectInt	netcoreapp31	.NET Core 3.1	192.2510 ns	2.3691 ns	2.1002 ns	191.4821 ns	85.061	2.88	8
GetterString	netcoreapp31	.NET Core 3.1	16.9918 ns	0.2115 ns	0.1979 ns	16.9651 ns	7.516	0.25	5
GetterInt	netcoreapp31	.NET Core 3.1	16.1168 ns	0.3558 ns	0.3654 ns	15.9822 ns	7.138	0.19	4
GetterObject	netcoreapp31	.NET Core 3.1	19.3060 ns	0.4173 ns	0.5571 ns	19.4856 ns	8.480	0.45	6
GetterCached	netcoreapp31	.NET Core 3.1	2.9276 ns	0.0156 ns	0.0146 ns	2.9313 ns	1.295	0.03	3
DirectlyString	netcoreapp5	.NET Core 5.0	2.2455 ns	0.0084 ns	0.0078 ns	2.2460 ns	1.000	0.00	2
DirectlyInt	netcoreapp5	.NET Core 5.0	0.0000 ns	0.0000 ns	0.0000 ns	0.0000 ns	0.000	0.00	1
ReflectString	netcoreapp5	.NET Core 5.0	162.8780 ns	0.7135 ns	0.6674 ns	162.8741 ns	72.538	0.45	7
ReflectInt	netcoreapp5	.NET Core 5.0	171.1380 ns	0.4173 ns	0.3699 ns	171.1414 ns	76.217	0.31	8
GetterString	netcoreapp5	.NET Core 5.0	8.6244 ns	0.1891 ns	0.1769 ns	8.5469 ns	3.841	0.08	5
GetterInt	netcoreapp5	.NET Core 5.0	6.5511 ns	0.0347 ns	0.0325 ns	6.5634 ns	2.917	0.02	4
GetterObject	netcoreapp5	.NET Core 5.0	9.0732 ns	0.0306 ns	0.0272 ns	9.0735 ns	4.041	0.02	6
GetterCached	netcoreapp5	.NET Core 5.0	2.8223 ns	0.0728 ns	0.0681 ns	2.8190 ns	1.257	0.03	3

总结

使用表达式创建委托来取代 PropertyInfo 读取和写入属性效果很好。

开发者也可以直接引用 Newbe.ObjectVisitor 包来使用已经封装好的 ValueGetter 和 ValueSetter。

我只是知识的搬运工

- [晚绑定场景下对象属性赋值和取值可以不需要 PropertyInfo](https://www.cnblogs.com/artech/archive/2011/03/24/PropertyAccessor.html)

- [三种属性操作性能比较：PropertyInfo + Expression Tree + Delegate.CreateDelegate](https://www.cnblogs.com/artech/archive/2011/03/26/Propertyaccesstest.html)

- [关于 Expression Tree 和 IL Emit 的所谓的"性能差别"](https://www.cnblogs.com/artech/archive/2011/03/27/ExpressTreeVsIlEmit.html)