属性选择器表达式来; Func键< T>&GT ;.如何获取/设置值选定属性 [英] Property selector Expression<Func<T>>. How to get/set value to selected property

问题描述

我有我想在这样的方式来构造一个对象：

 无功富=新FancyObject（客户，C = GT; c.Email）; //客户有email属性
  

我应该如何申报的第二个参数？

如何将访问选定的setter / getter属性将类似于代码？

UPD。有在具有电子邮件属性模型几个实体。所以，可能是签名将是这样的：

 公共FancyObject（实体保持架，表达式来; Func键< T>>选择器）
  

和构造函数调用

 无功富=新FancyObject（客户，（）=> customer.Email）; 
  

解决方案

参数将是表达式来; Func键<客户，串>>选择。阅读它可以通过平编译：

  Func键<客户，串> FUNC = selector.Compile（）; 
  

即可进入 FUNC（客户） 。分配是棘手;简单的选择您可能希望你可以简单地分解为：

  VAR道具=（的PropertyInfo）（（MemberExpression）selector.Body ）。会员; 
 prop.SetValue（客户，为newValue，NULL）; 
  

但更复杂的表达式要么需要人工树散步，或某些4.0表达式节点类型

 表达式来; Func键<客户，串>>电子邮件
 =卡斯特= GT; cust.Email; 
 
变种为newValue = Expression.Parameter（email.Body.Type）; 
 VAR分配= Expression.Lambda<作用<客户，串>>（
 Expression.Assign（email.Body，为newValue），
 email.Parameters [0]，为newValue）; 
 
 VAR吸气= email.Compile（）; 
 VAR二传手= assign.Compile（）; 
  

I have an object that I want to be constructed in such manner:

var foo = new FancyObject(customer, c=>c.Email); //customer has Email property

How should I declare second parameter?

How the code that will access selected property setter/getter will look like?

Upd. There are several entities in the model that has Email property. So probably the signature will looks like:

public FancyObject(Entity holder, Expression<Func<T>> selector)

and the constructor call

var foo = new FancyObject(customer, ()=>customer.Email);

解决方案

The parameter would be an Expression<Func<Customer,string>> selector. Reading it can be via flat compile:

 Func<Customer,string> func = selector.Compile();

then you can access func(customer). Assigning is trickier; for simple selectors your could hope that you can simply decompose to:

var prop = (PropertyInfo)((MemberExpression)selector.Body).Member;
prop.SetValue(customer, newValue, null);

But more complex expressions would either need a manual tree walk, or some of the 4.0 expression node-types:

        Expression<Func<Customer, string>> email
             = cust => cust.Email;

        var newValue = Expression.Parameter(email.Body.Type);
        var assign = Expression.Lambda<Action<Customer, string>>(
            Expression.Assign(email.Body, newValue),
            email.Parameters[0], newValue);

        var getter = email.Compile();
        var setter = assign.Compile();

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