我可以得到特定的元数据从Func键＆LT; T，对象＆gt ;? [英] Can I get specific metadata from a Func<T, object>?

问题描述

考虑以下code：

string propertyName;
var dateList = new List<DateTime>() { DateTime.Now };
propertyName = dateList.GetPropertyName(dateTimeObject => dateTimeObject.Hour);

// I want the propertyName variable to now contain the string "Hour"

下面是扩展方法：

public static string GetPropertyName<T>(this IList<T> list, Func<T, object> func) {
   //TODO: would like to dynamically determine which 
   // property is being used in the func function/lambda
}

有没有办法做到这一点？我想，也许这另一种方法，使用防爆pression＆LT; Func键＆LT; T，对象＆gt;＆GT; 而不是 Func键＆LT; T，对象＆gt; 会给我更多的力量找到我所需要的，但我很茫然如何。

Is there a way to do this? I thought that maybe this other method, using Expression<Func<T, object>> instead of Func<T, object> would give me more power to find what I need, but I am at a loss at how.

public static string GetPropertyName<T>(this IList<T> list, Expression<Func<T, object>> expr) {
   // interrogate expr to get what I want, if possible
}

这是我第一次做这个事情深，LINQ的，所以也许我失去了一些东西明显。基本上我想传递lambda表达式的想法，让我得到编译时检查，但我不知道我的，我怎么能使用他们在这种特殊情况下的想法会工作。

This is the first time I have done anything this deep with Linq, so maybe I am missing something obvious. Basically I like the idea of passing in lambdas, so that I get compile-time checking, but I don't know that my idea on how I can use them in this particular case will work.

感谢

推荐答案

这是我使用的版本，它返回一个的PropertyInfo ，但得到这个名字实在是微不足道。

This is the version I use, it returns a PropertyInfo, but getting the name is trivial.

public static PropertyInfo GetProperty<T>(Expression<Func<T, object>> expression)  
{
    MemberExpression memberExpression = null;

    if (expression.Body.NodeType == ExpressionType.Convert)
    {
        memberExpression = ((UnaryExpression) expression.Body).Operand as MemberExpression;
    }
    else if (expression.Body.NodeType == ExpressionType.MemberAccess)
    {
        memberExpression = expression.Body as MemberExpression;
    }

    if (memberExpression == null)
    {
        throw new ArgumentException("Not a member access", "expression");
    }

    return memberExpression.Member as PropertyInfo;
}

这篇关于我可以得到特定的元数据从Func键＆LT; T，对象＆gt ;?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！