通过表达式目录树拼装lambda表达式，来实现两个类型的复制

一、下面的方法实现两个类型间的值复制

    /// <summary>
    /// 交换两个类型的属性（复制）
    /// </summary>
    /// <typeparam name="Tin"></typeparam>
    /// <typeparam name="Tout"></typeparam>
    public static class ExpressionCopy<Tin, Tout>
    {
        public static Tout Excharnge(Tin tin)
        {
            ParameterExpression experssionin = Expression.Parameter(typeof(Tin), "tModel");//创建实例
            List<MemberBinding> memberList = new List<MemberBinding>();//通过绑定用的
            foreach (var item in typeof(Tout).GetFields())//遍历所有的共有字段
            {
                FieldInfo field = typeof(Tin).GetField(item.Name.GetPropertyRemark(typeof(Tout), 1));
                if (field != null)
                {
                    MemberExpression member = Expression.Field(experssionin, field);
                    MemberBinding binding = Expression.Bind(item, member);
                    memberList.Add(binding);
                }
            }  

            foreach (var item in typeof(Tout).GetProperties())//遍历属性
            {
                PropertyInfo pro = typeof(Tin).GetProperty(item.Name.GetPropertyRemark(typeof(Tout), 2));//判断属性是否存在
                if (pro != null)
                {
                    MemberExpression proper = Expression.Property(experssionin, pro);
                    MemberBinding binding = Expression.Bind(item, proper);
                    memberList.Add(binding);
                }  

            }  

            MemberInitExpression init = Expression.MemberInit(Expression.New(typeof(Tout)), memberList.ToArray());//初始化绑定新成员
            Expression<Func<Tin, Tout>> lambda = Expression.Lambda<Func<Tin, Tout>>(init, new ParameterExpression[]
            {
            experssionin
            });
            return lambda.Compile().Invoke(tin);
        }
    }  

二、声明特性为了防止当要复制的属性字段不一致

/// <summary>
    /// 特性
    /// </summary>
    public class GetRemarkAttribute : Attribute
    {
        public GetRemarkAttribute(string name)
        {
            this._remark = name;
        }
        private string _remark;
        public string GetRemark()
        {
            return _remark;
        }
    }  

三、通过反射为string类型添加一个扩展方法，来获取特性的值

 1 public static class GetRemark
 2    {
 3        /// <summary>
 4        /// 通过反射获得特性
 5        /// </summary>
 6        /// <param name="values">字段属性名称</param>
 7        /// <param name="type">类型</param>
 8        /// <param name="parameter">参数1为字段2为属性</param>
 9        /// <returns></returns>
10        public static string GetPropertyRemark(this string values, Type type, int parameter)
11        {
12            if (parameter == 1)
13            {
14                FieldInfo propperty = type.GetField(values);
15
16                if (propperty.IsDefined(typeof(GetRemarkAttribute)))
17                {
18                    GetRemarkAttribute remark = (GetRemarkAttribute)propperty.GetCustomAttribute(typeof(GetRemarkAttribute));
19                    return remark.GetRemark();
20                }
21
22            }
23            else
24            {
25                PropertyInfo propperty = type.GetProperty(values);
26
27                if (propperty.IsDefined(typeof(GetRemarkAttribute)))
28                {
29                    GetRemarkAttribute remark = (GetRemarkAttribute)propperty.GetCustomAttribute(typeof(GetRemarkAttribute));
30                    return remark.GetRemark();
31                }
32
33            }
34            return values;
35
36        }
37    }  

四、下面就是实际操作调用

 1 public class OldPersoninfo
 2     {
 3         public int Id { get; set; }
 4         public string Name { get; set; }
 5         public string Type { get; set; }
 6         public OldPersoninfo()
 7         {
 8             Id = 2;
 9             Name = "测试";
10             Type = "非常类额";
11         }
12     }
13     public class NewPersoninfo
14     {
15         public int Id { get; set; }
16        // [GetRemark("Name")]
17         public string newName { get; set; }
18         //[GetRemark("Type")]
19         public string newType { get; set; }
20     }
21
22
23 private void test_Load(object sender, EventArgs e)
24        {
25            OldPersoninfo old = new OldPersoninfo();
26            NewPersoninfo newPersoninfo = ExpressionCopy<OldPersoninfo, NewPersoninfo>.Excharnge(old);
27            MessageBox.Show(newPersoninfo.newType);
28        }  

原文地址：https://www.cnblogs.com/xiaojunwu/p/11811829.html