typeof() 有效，GetType() 在检索属性时无效 [英] typeof() works, GetType() doesn't works when retrieving property

问题描述

我正在尝试通过反射检索 private 属性的值

I am trying to retrieve a value of private property via reflection

// definition
public class Base
{
    private bool Test { get { return true; } }
}
public class A: Base {}
public class B: Base {}

// now
object obj = new A(); // or new B()

// works
var test1 = typeof(Base).GetProperty("Test", BindingFlags.Instance | BindingFlags.NonPublic);
if(test1 != null) // it's not null
    if((bool)test1.GetValue(obj, null)) // it's true
        ...

// doesn't works!
var test2 = obj.GetType().GetProperty("Test", BindingFlags.Instance | BindingFlags.NonPublic);
if(test2 != null) // is null !
    ...

我的错误在哪里?我将需要使用 object 来传递实例，因为一些 private 属性将在 A 或 B 中声明>.有时甚至隐藏(使用 new)Base 属性.

Where is my mistake? I will need to use object to pass instance, because some of private properties will be declared in the A or B. And even hiding (with new) Base properties sometimes.

推荐答案

Test 是 Base 私有的.它对继承的 A/B 类不可见.如果你想让它对继承类可见，你应该让它protected.

Test is private to Base. It is not visible to the inherited A/B classes. You should make it protected if you want it visible to the inheriting class.

或者如果继承树只有一层，你可以使用GetType().BaseType.

Or you can use GetType().BaseType if the inheritance tree is just one level.

public class Base
{
    private bool Test { get { return true; } }
    protected bool Test2 { get { return true; } }
}
public class A : Base { }
public class B : Base { }

[TestMethod]
public void _Test()
{
    object obj = new A(); // or new B()         

    Assert.IsNotNull(typeof(Base).GetProperty("Test", BindingFlags.Instance | BindingFlags.NonPublic));
    Assert.IsNotNull(typeof(Base).GetProperty("Test2", BindingFlags.Instance | BindingFlags.NonPublic));

    Assert.IsNull(typeof(A).GetProperty("Test", BindingFlags.Instance | BindingFlags.NonPublic));
    Assert.IsNotNull(typeof(A).GetProperty("Test2", BindingFlags.Instance | BindingFlags.NonPublic));

    Assert.IsNull(typeof(A).GetProperty("Test", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.FlattenHierarchy));
    Assert.IsNotNull(typeof(A).GetProperty("Test2", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.FlattenHierarchy));

    Assert.IsNull(obj.GetType().GetProperty("Test", BindingFlags.Instance | BindingFlags.NonPublic));
    Assert.IsNotNull(obj.GetType().GetProperty("Test2", BindingFlags.Instance | BindingFlags.NonPublic));

    Assert.IsNotNull(obj.GetType().BaseType.GetProperty("Test", BindingFlags.Instance | BindingFlags.NonPublic));
    Assert.IsNotNull(obj.GetType().BaseType.GetProperty("Test2", BindingFlags.Instance | BindingFlags.NonPublic));

}

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