反思大师:为什么我的MethodInfo对象不相等？

Question

基本上,静态System.Linq.Expressions.Expression.Bind()方法中发生的一些内部检查在我的属性上显示"方法不是属性访问器",显然是属性.使用Reflector,我已经最小化了导致问题的代码量,而且我不能为我的生活找出为什么会发生这种情况.我唯一的猜测是它与属性不在类本身上这一事实有关,但我认为这应该仍然有效:

我试图用尽可能少的代码做一个小例子.下面的代码应该完整运行.

using System;
using System.Reflection;

public class Base
{
    public virtual int Id { get; set; }
}

// As you can see, SubClass does not override the Id property of Base.
public class SubClass : Base { }

class Program
{
    static void Main(string[] args)
    {
        // Getting the property directly from the type.
        PropertyInfo propertyInfo = typeof(SubClass).GetProperty("Id");
        MethodInfo setMethod = propertyInfo.GetSetMethod();

        /*  Code from here on out is from the System.Linq.Expressions.Bind() method (the one
            that accepts a MethodInfo argument). This method causes GetProperty to be called
            and retrieve what should be the same PropertyInfo. It fails here, saying something
            along the lines of "Method is not a property accessor." which doesn't make sense. */
        PropertyInfo propertyInfo2 = GetProperty(setMethod);
    }

    private static PropertyInfo GetProperty(MethodInfo mi)
    {
        // Not sure if it matters, but declaringType here is "Base".
        Type declaringType = mi.DeclaringType;

        BindingFlags bindingAttr = BindingFlags.NonPublic | BindingFlags.Public;
        bindingAttr |= mi.IsStatic ? BindingFlags.Static : BindingFlags.Instance;

        foreach (PropertyInfo info in declaringType.GetProperties(bindingAttr))
        {
            // For the "Id" property, info.CanRead is true, but CheckMethod is false.
            if (info.CanRead && CheckMethod(mi, info.GetGetMethod(true)))
                return info;

            // For the "Id" property, info.CanWrite is true, but CheckMethod is false.
            if (info.CanWrite && CheckMethod(mi, info.GetSetMethod(true)))
                return info;
        }

        // This gets thrown after passing by the "Id" property that is the one I'm looking for.
        throw new Exception("Method is not a property accessor");
    }

    private static bool CheckMethod(MethodInfo method, MethodInfo propertyMethod)
    {
        // These are not equal, so it goes to the next check. In the debugger, they appear identical when I look through the object tree.
        if (method == propertyMethod)
            return true;

        Type declaringType = method.DeclaringType;
        return ((declaringType.IsInterface && (method.Name == propertyMethod.Name)) && (declaringType.GetMethod(method.Name) == propertyMethod));
    }
}

如果有人能帮助我会非常感激!我现在非常失落.

编辑-如果你替换typeof(SubClass)用typeof(Base),它的工作原理,所以它的东西涉及到这种关系.我想我可以通过制作扩展方法来解决问题,typeof(SubClass).GetPropertyFromActualClass("Id")但我不知道如何执行该检查.

Answer 1

Base和SubClass的属性和方法信息确实不相等,即使SubClass没有自己的实现,如下所示:

var subPropertyInfo = typeof(SubClass).GetProperty("Id");
var subPropertyInfoSetter = subPropertyInfo.GetSetMethod();

var basePropertyInfo = typeof(Base).GetProperty("Id");
var basePropertyInfoSetter = basePropertyInfo.GetSetMethod();

Console.WriteLine(subPropertyInfo == basePropertyInfo);     // false
Console.WriteLine(subPropertyInfoSetter == basePropertyInfoSetter); // false

如果您使用mi.ReflectedType而不是mi.DeclaringType,则检查成功:

var type = subPropertyInfoSetter.ReflectedType;
Console.WriteLine(type.GetProperty("Id").GetSetMethod() 
                               == subPropertyInfoSetter); // true