访问类保护字段而不修改原始类 [英] Accessing a class protected field without modifying original class

问题描述

我正在使用一些公开某种类型(由方法返回)的第三方库.

I am using some 3rd party library that exposes some type (returned by a method).

此类型具有一些我感兴趣的受保护字段，但是由于其可见性受保护，因此我无法使用它们.

This type has some protected fields i am interested in, however i am not able to use them since their visibility is protected.

这是问题的简化:

public class A
    {
        protected object Something;

        public A Load()
        {
            return new A();
        }
    }

    public class ExtendedA : A
    {
        public void DoSomething()
        {
            // Get an instance.
            var a = Load();

            // Access protected fields (doesn't compile).
            a.Something = ....
        }
    }

有什么简单的方法可以实现这一目标吗?

Is there any easy way to achieve this?

推荐答案

说明

您可以使用this.Something访问该字段，因为您的课程是从class A派生的.

Description

You can access the Field using this.Something because your class is derived from class A.

如果要创建class A的实例而不是派生类，则只能使用反射来访问该字段.

If you want to create a instance of the class A, not your derived class, you can only access the field using reflection.

public class ExtendedA : A
{
    public void DoSomething()
    {
        // Get an instance.
        var a = Load();

        //get the type of the class
        Type type = a.GetType();
        BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.NonPublic;

        // get the field info
        FieldInfo finfo = type.GetField("Something", bindingFlags);

        // set the value 
        finfo.SetValue(a, "Hello World!");

        // get the value
        object someThingField = finfo.GetValue(a);
    }
}

更多信息

• 通过反射访问受保护的属性和字段

More Information

• Accessing Protected Properties and Fields with Reflection

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