c# - 如何强制开发人员将属性应用于类？

Question

我正在创建一个基类。我希望如果它被某个派生类继承，它必须应用一个属性，否则会抛出编译错误。可能吗？

public class MyAttribte : Attribute
{
    public string TestString {get; set; }
}

public class Base
{
}

/*Attribute must be applied else throw compile time error.*/
[MyAttribte]
public class Derived : Base { }

Answer 1

你不能强制，但如果未指定 Attribute，你可以在运行时检查并抛出异常。

var d1 = new Derived1(); // OK
var d2 = new Derived2(); // throw error at run-time

public class Base
{
    public Base()
    {
        CheckCustomAttribute();

    }

    private void CheckCustomAttribute()
    {
        if (!(this.GetType() == typeof(Base))) // Ingore Base for attribute
        {
            //  var attr = System.Attribute.GetCustomAttributes(this.GetType()).SingleOrDefault(t=>t.GetType() == typeof(CustomAttribute));
            var attr = System.Attribute.GetCustomAttributes(this.GetType()).SingleOrDefault(t => typeof(CustomAttribute).IsAssignableFrom(t.GetType())); // to include derived type of Custom attribute also
            if (attr == null)
            {
                throw new Exception(String.Format("Derived class {0} doesnot apply {1} attribute", this.GetType().Name, typeof(CustomAttribute).Name));
            }
        }
    }
}

[CustomAttribute]
class Derived1 : Base
{
}

class Derived2 : Base
{
}
class CustomAttribute : System.Attribute
{
}