我有一个类,叫它Book,它的属性叫Name。有了这个属性,我就有了一个与之关联的属性。

public class Book
{
    [Author("AuthorName")]
    public string Name
    {
        get; private set; 
    }
}

在我的主要方法中,我使用反射,并希望获得每个属性的每个属性的键值对。因此,在本例中,我希望看到属性名为“Author”,属性值为“AuthorName”。

问:如何使用反射获取属性上的属性名和值?


当前回答

要获取一个属性在字典中的所有属性,请使用以下命令:

typeof(Book)
  .GetProperty("Name")
  .GetCustomAttributes(false) 
  .ToDictionary(a => a.GetType().Name, a => a);

如果您还想包含继承的属性,请记住从false更改为true。

其他回答

private static Dictionary<string, string> GetAuthors()
{
    return typeof(Book).GetProperties()
        .SelectMany(prop => prop.GetCustomAttributes())
        .OfType<AuthorAttribute>()
        .ToDictionary(a => a.GetType().Name.Replace("Attribute", ""), a => a.Name);
}

使用泛型的示例(目标框架4.5)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

private static Dictionary<string, string> GetAttribute<TAttribute, TType>(
    Func<TAttribute, string> valueFunc)
    where TAttribute : Attribute
{
    return typeof(TType).GetProperties()
        .SelectMany(p => p.GetCustomAttributes())
        .OfType<TAttribute>()
        .ToDictionary(a => a.GetType().Name.Replace("Attribute", ""), valueFunc);
}

使用

var dictionary = GetAttribute<AuthorAttribute, Book>(a => a.Name);
public static class PropertyInfoExtensions
{
    public static TValue GetAttributValue<TAttribute, TValue>(this PropertyInfo prop, Func<TAttribute, TValue> value) where TAttribute : Attribute
    {
        var att = prop.GetCustomAttributes(
            typeof(TAttribute), true
            ).FirstOrDefault() as TAttribute;
        if (att != null)
        {
            return value(att);
        }
        return default(TValue);
    }
}

用法:

 //get class properties with attribute [AuthorAttribute]
        var props = typeof(Book).GetProperties().Where(prop => Attribute.IsDefined(prop, typeof(AuthorAttribute)));
            foreach (var prop in props)
            {
               string value = prop.GetAttributValue((AuthorAttribute a) => a.Name);
            }

or:

 //get class properties with attribute [AuthorAttribute]
        var props = typeof(Book).GetProperties().Where(prop => Attribute.IsDefined(prop, typeof(AuthorAttribute)));
        IList<string> values = props.Select(prop => prop.GetAttributValue((AuthorAttribute a) => a.Name)).Where(attr => attr != null).ToList();
foreach (var p in model.GetType().GetProperties())
{
   var valueOfDisplay = 
       p.GetCustomAttributesData()
        .Any(a => a.AttributeType.Name == "DisplayNameAttribute") ? 
            p.GetCustomAttribute<DisplayNameAttribute>().DisplayName : 
            p.Name;
}

在这个例子中,我使用DisplayName而不是Author,因为它有一个名为“DisplayName”的字段要显示一个值。

使用typeof(Book). getproperties()获取PropertyInfo实例数组。然后对每个PropertyInfo使用GetCustomAttributes()来查看它们中是否有Author Attribute类型。如果有,您可以从属性信息中获得属性的名称,并从属性中获得属性值。

沿着这些行来扫描类型中具有特定属性类型的属性,并在字典中返回数据(注意,通过将类型传递到例程中,这可以变得更加动态):

public static Dictionary<string, string> GetAuthors()
{
    Dictionary<string, string> _dict = new Dictionary<string, string>();

    PropertyInfo[] props = typeof(Book).GetProperties();
    foreach (PropertyInfo prop in props)
    {
        object[] attrs = prop.GetCustomAttributes(true);
        foreach (object attr in attrs)
        {
            AuthorAttribute authAttr = attr as AuthorAttribute;
            if (authAttr != null)
            {
                string propName = prop.Name;
                string auth = authAttr.Name;

                _dict.Add(propName, auth);
            }
        }
    }

    return _dict;
}

我已经通过编写一个通用扩展属性属性助手解决了类似的问题:

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

public static class AttributeHelper
{
    public static TValue GetPropertyAttributeValue<T, TOut, TAttribute, TValue>(
        Expression<Func<T, TOut>> propertyExpression, 
        Func<TAttribute, TValue> valueSelector) 
        where TAttribute : Attribute
    {
        var expression = (MemberExpression) propertyExpression.Body;
        var propertyInfo = (PropertyInfo) expression.Member;
        var attr = propertyInfo.GetCustomAttributes(typeof(TAttribute), true).FirstOrDefault() as TAttribute;
        return attr != null ? valueSelector(attr) : default(TValue);
    }
}

用法:

var author = AttributeHelper.GetPropertyAttributeValue<Book, string, AuthorAttribute, string>(prop => prop.Name, attr => attr.Author);
// author = "AuthorName"