从ViewModel获取[key]属性 [英] Get [key] property from ViewModel

问题描述

我有一个具有[key]属性的ViewModel，我想从该视图模型的实例中获取它.

I have a ViewModel which has a [key] property and i would like to get that from an instance of that view model.

我的代码看起来像这样(虚构模型)

My code looks something like this (fictional models)

class AddressViewModel
{
    [Key]
    [ScaffoldColumn(false)]
    public int UserID { get; set; } // Foreignkey to UserViewModel
}

// ... somewhere else i do:
var addressModel = new AddressViewModel();
addressModel.HowToGetTheKey..??

所以我需要从ViewModel中获取UserID(在这种情况下).我该怎么办?

So i need to get the UserID(in this case) from the ViewModel. How can i do this?

推荐答案

_{如果您对示例中的任何代码感到困惑或困惑，请添加注释，我将尽力提供帮助.}

总而言之，您很有趣地使用 Reflection 遍历该类型的元数据以获得具有为其分配了给定属性的属性.

In summary, you are interesting in using Reflection to walk the meta-data of the type to get properties that have a given attribute assigned to them.

下面只是实现此目的的一种方法(有许多其他方法，也有许多提供相似功能的方法).

Below is just one way of doing this (there are many others and also many methods that provide similar functionality).

来自这个问题评论:

PropertyInfo[] properties = viewModelInstance.GetType().GetProperties();

foreach (PropertyInfo property in properties)
{
    var attribute = Attribute.GetCustomAttribute(property, typeof(KeyAttribute)) 
        as KeyAttribute;

    if (attribute != null) // This property has a KeyAttribute
    {
         // Do something, to read from the property:
         object val = property.GetValue(viewModelInstance);
    }
}

像乔恩(Jon)所说，请处理多个KeyAttribute声明以避免出现问题.此代码还假定您正在修饰public属性(不是非公共属性或字段)，并且需要System.Reflection.

Like Jon says, handle multiple KeyAttribute declarations to avoid issues. This code also assumes you are decorating public properties (not, non-public properties or fields) and requires System.Reflection.

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