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：

  public class People
    {
        public int Age { get; set; }
        public string Name { get; set; }

        public int Id;

    }

PeopleCopy类：

namespace ConsoleApp2
{
    public class PeopleCopy
    {
        public int Age { get; set; }
        public string Name { get; set; }

        public int Id;

        public override string ToString()
        {
            return "Age="+Age+";Name="+Name+";Id="+Id;
        }
    }
}

实现类型属性赋值：ExpressionTree类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace ConsoleApp1
{
    public class Class1
    {
    
        private static Dictionary<string, object> _Dic = new Dictionary<string, object>();
        private static TOut TransExp<TIn, TOut>(TIn tIn)
        {
            string key = $"funckey_{typeof(TIn).FullName}_{typeof(TOut).FullName}";
            if (!_Dic.Keys.Contains(key))
            {
                ParameterExpression parameterExpression = Expression.Parameter(typeof(TIn), "p");
                List<MemberBinding> memberBindingList = new List<MemberBinding>();
                foreach (var item in typeof(TOut).GetProperties())
                {
                    PropertyInfo propertyInfo = typeof(TIn).GetProperty(item.Name);
                    if (propertyInfo == null) { continue; }
                    MemberExpression property = Expression.Property(parameterExpression, propertyInfo);
                    memberBindingList.Add(Expression.Bind(item, property));
                }
                foreach (var item in typeof(TOut).GetFields())
                {
                    FieldInfo fieldInfo = typeof(TIn).GetField(item.Name);
                    if (fieldInfo == null) { continue; }
                    MemberExpression property = Expression.Field(parameterExpression, fieldInfo);
                    memberBindingList.Add(Expression.Bind(item, property));
                }
                Expression<Func<TIn, TOut>> expression = Expression.Lambda<Func<TIn, TOut>>(Expression.MemberInit(Expression.New(typeof(TOut)), memberBindingList), new ParameterExpression[]
                {
parameterExpression
                });
                Func<TIn, TOut> func = expression.Compile();
                _Dic.Add(key, func);
            }
            return ((Func<TIn, TOut>)_Dic[key])(tIn);
        }

    }
}

 测试：Program类：

using System;
using System.Collections.Generic;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {

            List<PeopleCopy> peoleCopyList = new List<PeopleCopy>();
            for (int i = 0; i < 5; i++)
            {
                People people = new People() { Id = 5 + 1, Age = 25, Name = "aaa" + i };
                peoleCopyList.Add(ExpressionTree.TransExp<People, PeopleCopy>(people));
            }
            foreach (var item in peoleCopyList)
            {
                Console.WriteLine(item);
            }
            Console.Read();
        }
    }
}

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。