C#-使用属性名称作为字符串按属性排序的代码 [英] C# - code to order by a property using the property name as a string

问题描述

当我将属性名称作为字符串时，对C#中的属性进行编码的最简单方法是什么?例如，我想允许用户通过他们选择的属性(使用LINQ)对一些搜索结果进行排序.他们将在UI中选择"order by"属性-当然是字符串值.有没有一种方法可以直接使用该字符串作为linq查询的属性，而不必使用条件逻辑(如果/否则，切换)将字符串映射到属性.反思?

What's the simplest way to code against a property in C# when I have the property name as a string? For example, I want to allow the user to order some search results by a property of their choice (using LINQ). They will choose the "order by" property in the UI - as a string value of course. Is there a way to use that string directly as a property of the linq query, without having to use conditional logic (if/else, switch) to map the strings to properties. Reflection?

从逻辑上讲，这就是我想要做的:

Logically, this is what I'd like to do:

query = query.OrderBy(x => x."ProductId");

更新: 我最初并未指定我使用的是Linq to Entities-看来反射(至少是GetProperty，GetValue方法)不能转换为L2E.

Update: I did not originally specify that I'm using Linq to Entities - it appears that reflection (at least the GetProperty, GetValue approach) does not translate to L2E.

推荐答案

我将提供其他人发布的替代方案.

I would offer this alternative to what everyone else has posted.

System.Reflection.PropertyInfo prop = typeof(YourType).GetProperty("PropertyName");

query = query.OrderBy(x => prop.GetValue(x, null));

这避免了为获得该属性而重复调用反射API.现在唯一的重复调用就是获取值.

This avoids repeated calls to the reflection API for obtaining the property. Now the only repeated call is obtaining the value.

但是

我建议改为使用PropertyDescriptor，因为这将允许将自定义的TypeDescriptor分配给您的类型，从而可以进行轻量级的操作来检索属性和值.在缺少自定义描述符的情况下，无论如何它都会退回去反映.

I would advocate using a PropertyDescriptor instead, as this will allow for custom TypeDescriptors to be assigned to your type, making it possible to have lightweight operations for retrieving properties and values. In the absence of a custom descriptor it will fall back to reflection anyhow.

PropertyDescriptor prop = TypeDescriptor.GetProperties(typeof(YourType)).Find("PropertyName");

query = query.OrderBy(x => prop.GetValue(x));

要加快速度，请查看Marc Gravel的 HyperDescriptor 项目在CodeProject上.我已经成功地使用了它；它是针对业务对象进行高性能数据绑定和动态属性操作的救生器.

As for speeding it up, check out Marc Gravel's HyperDescriptor project on CodeProject. I've used this with great success; it's a life saver for high-performance data binding and dynamic property operations on business objects.

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