C# 类可以从其接口继承属性吗? [英] Can a C# class inherit attributes from its interface?

问题描述

这似乎意味着不".这是不幸的.

This would appear to imply "no". Which is unfortunate.

[AttributeUsage(AttributeTargets.Interface | AttributeTargets.Class,
 AllowMultiple = true, Inherited = true)]
public class CustomDescriptionAttribute : Attribute
{
    public string Description { get; private set; }

    public CustomDescriptionAttribute(string description)
    {
        Description = description;
    }
}

[CustomDescription("IProjectController")]
public interface IProjectController
{
    void Create(string projectName);
}

internal class ProjectController : IProjectController
{
    public void Create(string projectName)
    {
    }
}

[TestFixture]
public class CustomDescriptionAttributeTests
{
    [Test]
    public void ProjectController_ShouldHaveCustomDescriptionAttribute()
    {
        Type type = typeof(ProjectController);
        object[] attributes = type.GetCustomAttributes(
            typeof(CustomDescriptionAttribute),
            true);

        // NUnit.Framework.AssertionException:   Expected: 1   But was:  0
        Assert.AreEqual(1, attributes.Length);
    }
}

类可以从接口继承属性吗?还是我在这里吠错了树?

Can a class inherit attributes from an interface? Or am I barking up the wrong tree here?

推荐答案

没有.每当在派生类中实现接口或覆盖成员时，都需要重新声明属性.

No. Whenever implementing an interface or overriding members in a derived class, you need to re-declare the attributes.

如果你只关心 ComponentModel(而不是直接反射)，有一个方法([AttributeProvider]) 建议来自现有类型的属性(以避免重复)，但它仅对属性和索引器使用有效.

If you only care about ComponentModel (not direct reflection), there is a way ([AttributeProvider]) of suggesting attributes from an existing type (to avoid duplication), but it is only valid for property and indexer usage.

举个例子:

using System;
using System.ComponentModel;
class Foo {
    [AttributeProvider(typeof(IListSource))]
    public object Bar { get; set; }

    static void Main() {
        var bar = TypeDescriptor.GetProperties(typeof(Foo))["Bar"];
        foreach (Attribute attrib in bar.Attributes) {
            Console.WriteLine(attrib);
        }
    }
}

输出:

System.SerializableAttribute
System.ComponentModel.AttributeProviderAttribute
System.ComponentModel.EditorAttribute
System.Runtime.InteropServices.ComVisibleAttribute
System.Runtime.InteropServices.ClassInterfaceAttribute
System.ComponentModel.TypeConverterAttribute
System.ComponentModel.MergablePropertyAttribute

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