C#_表达式目录树的应用

使用表达式目录树实现两个不同类型的属性赋值：

People类：

1   public class People
2     {
3         public int Age { get; set; }
4         public string Name { get; set; }
5 
6         public int Id;
7 
8     }

View Code

PeopleCopy类：

 1 namespace ConsoleApp2
 2 {
 3     public class PeopleCopy
 4     {
 5         public int Age { get; set; }
 6         public string Name { get; set; }
 7 
 8         public int Id;
 9 
10         public override string ToString()
11         {
12             return "Age="+Age+";Name="+Name+";Id="+Id;
13         }
14     }
15 }

View Code

实现类型属性赋值：ExpressionTree类

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Linq.Expressions;
 5 using System.Reflection;
 6 
 7 namespace ConsoleApp1
 8 {
 9     public class Class1
10     {
11     
12         private static Dictionary<string, object> _Dic = new Dictionary<string, object>();
13         private static TOut TransExp<TIn, TOut>(TIn tIn)
14         {
15             string key = $"funckey_{typeof(TIn).FullName}_{typeof(TOut).FullName}";
16             if (!_Dic.Keys.Contains(key))
17             {
18                 ParameterExpression parameterExpression = Expression.Parameter(typeof(TIn), "p");
19                 List<MemberBinding> memberBindingList = new List<MemberBinding>();
20                 foreach (var item in typeof(TOut).GetProperties())
21                 {
22                     PropertyInfo propertyInfo = typeof(TIn).GetProperty(item.Name);
23                     if (propertyInfo == null) { continue; }
24                     MemberExpression property = Expression.Property(parameterExpression, propertyInfo);
25                     memberBindingList.Add(Expression.Bind(item, property));
26                 }
27                 foreach (var item in typeof(TOut).GetFields())
28                 {
29                     FieldInfo fieldInfo = typeof(TIn).GetField(item.Name);
30                     if (fieldInfo == null) { continue; }
31                     MemberExpression property = Expression.Field(parameterExpression, fieldInfo);
32                     memberBindingList.Add(Expression.Bind(item, property));
33                 }
34                 Expression<Func<TIn, TOut>> expression = Expression.Lambda<Func<TIn, TOut>>(Expression.MemberInit(Expression.New(typeof(TOut)), memberBindingList), new ParameterExpression[]
35                 {
36 parameterExpression
37                 });
38                 Func<TIn, TOut> func = expression.Compile();
39                 _Dic.Add(key, func);
40             }
41             return ((Func<TIn, TOut>)_Dic[key])(tIn);
42         }
43 
44     }
45 }

View Code

测试：Program类：

 1 using System;
 2 using System.Collections.Generic;
 3 
 4 namespace ConsoleApp2
 5 {
 6     class Program
 7     {
 8         static void Main(string[] args)
 9         {
10 
11             List<PeopleCopy> peoleCopyList = new List<PeopleCopy>();
12             for (int i = 0; i < 5; i++)
13             {
14                 People people = new People() { Id = 5 + 1, Age = 25, Name = "aaa" + i };
15                 peoleCopyList.Add(ExpressionTree.TransExp<People, PeopleCopy>(people));
16             }
17             foreach (var item in peoleCopyList)
18             {
19                 Console.WriteLine(item);
20             }
21             Console.Read();
22         }
23     }
24 }

View Code

结果如下：

ExpressionTreeVisualize for vs2017

Expression Tree Visualizer 是一个集成在Visual Studio中的工具，用于在运行时以树状结构显示出指定的Expression。

明天你会感激你今天所做的努力。