为通用约束使用属性 [英] Using Attributes for Generic Constraints

问题描述

举个例子，比如..

public interface IInterface { }

public static void Insert<T>(this IList<T> list, IList<T> items) where T : IInterface
{
 // ... logic
}

这很好用，但我想知道是否可以使用属性作为约束.比如……

This works fine, but I was wondering if it is possible to use an Attribute as a constraint. Such as ...

class InsertableAttribute : Attribute

public static void Insert<T>(this IList<T> list, IList<T> items) where T : [Insertable]
{
 // ... logic
}

显然这种语法不起作用，否则我不会发布问题.但我只是好奇这是否可能，以及如何做到这一点.

Obviously this syntax doesn't work, or I wouldn't be posting the question. But I'm just curious if it is possible or not, and how to do it.

推荐答案

不可以.你只能使用(基)类和接口作为约束.

No. You can only use (base)classes and interfaces as constraints.

但是你可以这样做:

public static void Insert<T>(this IList<T> list, IList<T> items)
{
    var attributes = typeof(T).GetCustomAttributes(typeof(InsertableAttribute), true);

    if (attributes.Length == 0)
        throw new ArgumentException("T does not have attribute InsertableAttribute");

    /// Logic.
}

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