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该属性本身不属于该类的事实有关，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地运行。

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));
    }
}

如果有人能提供帮助我会非常感激！我现在非常迷失。

修改 - 如果您将typeof(SubClass)替换为typeof(Base)，它就会起作用，因此它与该关系相关。我想我可以通过制作像typeof(SubClass).GetPropertyFromActualClass("Id")这样的扩展方法来解决问题，但我不确定如何执行该检查。

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，也可以在这里看到：

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

反思大师：为什么我的MethodInfo对象不相等？

1 个答案: