获取抽象类的所有继承类 [英] Get all inherited classes of an abstract class

问题描述

我有一个抽象类:

abstract class AbstractDataExport
{
        public string name;
        public abstract bool ExportData();
}

我有从 AbstractDataExport 派生的类:

I have classes which are derived from AbstractDataExport:

class XmlExport : AbstractDataExport
{
    new public string name = "XmlExporter";
    public override bool ExportData()
    {
        ...
    }
}
class CsvExport : AbstractDataExport
{
    new public string name = "CsvExporter";
    public override bool ExportData()
    {
        ...
    }
}

有没有可能做这样的事情?(伪代码:)

Is it possible to do something like this? (Pseudocode:)

foreach (Implementation imp in Reflection.GetInheritedClasses(AbstractDataExport)
{
    AbstractDataExport derivedClass = Implementation.CallConstructor();
    Console.WriteLine(derivedClass.name)
}

具有类似的输出

CsvExporter
XmlExporter

?

这背后的想法是创建一个从 AbstractDataExport 派生的新类，这样我就可以自动遍历所有实现并将名称添加到下拉列表中.只想对派生类进行编码，项目中不做任何改动，重新编译，bingo！

The idea behind this is to just create a new class which is derived from AbstractDataExport so i can iterate through all implementations automatically and add for example the names to a Dropdown-List. I just want to code the derived class without changing anything else in the project, recompile, bingo!

如果您有其他解决方案:告诉他们.

If you have alternative solutions: tell em.

谢谢

推荐答案

这是一个很常见的问题，尤其是在 GUI 应用程序中，我很惊讶没有一个 BCL 类可以开箱即用.这是我的做法.

This is such a common problem, especially in GUI applications, that I'm surprised there isn't a BCL class to do this out of the box. Here's how I do it.

public static class ReflectiveEnumerator
{
    static ReflectiveEnumerator() { }

    public static IEnumerable<T> GetEnumerableOfType<T>(params object[] constructorArgs) where T : class, IComparable<T>
    {
        List<T> objects = new List<T>();
        foreach (Type type in 
            Assembly.GetAssembly(typeof(T)).GetTypes()
            .Where(myType => myType.IsClass && !myType.IsAbstract && myType.IsSubclassOf(typeof(T))))
        {
            objects.Add((T)Activator.CreateInstance(type, constructorArgs));
        }
        objects.Sort();
        return objects;
    }
}

一些注意事项:

• 不要担心此操作的成本" - 您只会执行一次(希望如此)，即便如此，它也不会像您想象的那么慢.
• 您需要使用 Assembly.GetAssembly(typeof(T))，因为您的基类可能位于不同的程序集中.
• 您需要使用条件 type.IsClass 和 !type.IsAbstract 因为如果您尝试实例化接口或抽象类，它会抛出异常.
• 我喜欢强制枚举类实现 IComparable 以便它们可以被排序.
• 您的子类必须具有相同的构造函数签名，否则会引发异常.这对我来说通常不是问题.

• Don't worry about the "cost" of this operation - you're only going to be doing it once (hopefully) and even then it's not as slow as you'd think.
• You need to use Assembly.GetAssembly(typeof(T)) because your base class might be in a different assembly.
• You need to use the criteria type.IsClass and !type.IsAbstract because it'll throw an exception if you try to instantiate an interface or abstract class.
• I like forcing the enumerated classes to implement IComparable so that they can be sorted.
• Your child classes must have identical constructor signatures, otherwise it'll throw an exception. This typically isn't a problem for me.

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