c# - "override"有没有办法用反射的方法？

Question

没有继承，只有反射，是否可以在C#中动态更改方法的代码？

类似的东西:

nameSpaceA.Foo.method1 = aDelegate;

我无法更改/编辑 Foo 类。

namespace nameSpaceA
{
  class Foo
  {
       private void method1()
       {
           // ... some Code
       }
  }
}

我的最终目标是动态更改以下代码:

public static IList<XPathNavigator> EnsureNodeSet(IList<XPathItem> listItems);

在 System.Xml.Xsl.Runtime.XslConvert.cs 中

转向:

if (!item.IsNode)
    throw new XslTransformException(Res.XPath_NodeSetExpected, string.Empty); 

进入:

if (!item.IsNode)
    throw new XslTransformException(Res.XPath_NodeSetExpected, item.value); 

Answer 1

这个答案的第一部分是错误的，我只是留下它，以便评论中的演变有意义。请参阅编辑。

您不是在寻找反射，而是在寻找发射(恰恰相反)。

特别是，有一种方法可以满足您的需求，您真幸运!

参见 TypeBuilder.DefineMethodOverride

编辑:
写这个答案，我只记得re-mix也允许您这样做。不过要难得多。

Re-mix 是一个在 C# 中“模拟”mixin 的框架。在其基本方面，您可以将其视为具有默认实现的接口(interface)。如果你走得更远，它会变得更多。

编辑 2:这是一个用于重新混合的示例(在不支持它且不知道混入的类上实现 INotifyPropertyChanged)。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Remotion.Mixins;
using System.ComponentModel;
using MixinTest;

[assembly: Mix(typeof(INPCTester), typeof(INotifyPropertyChangedMixin))]

namespace MixinTest
{
    //[Remotion.Mixins.CompleteInterface(typeof(INPCTester))]
    public interface ICustomINPC : INotifyPropertyChanged
    {
        void RaisePropertyChanged(string prop);
    }

    //[Extends(typeof(INPCTester))]
    public class INotifyPropertyChangedMixin : Mixin<object>, ICustomINPC
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void RaisePropertyChanged(string prop)
        {
             PropertyChangedEventHandler handler = this.PropertyChanged;
             if (handler != null)
             {
                 handler(this, new PropertyChangedEventArgs(prop));
             }
        }
    }

    public class ImplementsINPCAttribute : UsesAttribute 
    {
        public ImplementsINPCAttribute()
            : base(typeof(INotifyPropertyChangedMixin))
        {

        }
    }

    //[ImplementsINPC]
    public class INPCTester
    {
        private string m_Name;
        public string Name
        {
            get { return m_Name; }
            set
            {
                if (m_Name != value)
                {
                    m_Name = value;
                    ((ICustomINPC)this).RaisePropertyChanged("Name");
                }
            }
        }
    }

    public class INPCTestWithoutMixin : ICustomINPC
    {
        private string m_Name;
        public string Name
        {
            get { return m_Name; }
            set
            {
                if (m_Name != value)
                {
                    m_Name = value;
                    this.RaisePropertyChanged("Name");
                }
            }
        }

        public void RaisePropertyChanged(string prop)
        {
            PropertyChangedEventHandler handler = this.PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(prop));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}

和测试:

static void INPCImplementation()
        {
            Console.WriteLine("INPC implementation and usage");

            var inpc = ObjectFactory.Create<INPCTester>(ParamList.Empty);

            Console.WriteLine("The resulting object is castable as INPC: " + (inpc is INotifyPropertyChanged));

            ((INotifyPropertyChanged)inpc).PropertyChanged += inpc_PropertyChanged;

            inpc.Name = "New name!";
            ((INotifyPropertyChanged)inpc).PropertyChanged -= inpc_PropertyChanged;
            Console.WriteLine();
        }

static void inpc_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            Console.WriteLine("Hello, world! Property's name: " + e.PropertyName);
        }
//OUTPUT:
//INPC implementation and usage
//The resulting object is castable as INPC: True
//Hello, world! Property's name: Name

请注意:

[assembly: Mix(typeof(INPCTester), typeof(INotifyPropertyChangedMixin))]

和

[Extends(typeof(INPCTester))] //commented out in my example

和

[ImplementsINPC] //commented out in my example

具有完全相同的效果。这是您希望在何处定义特定混合应用到特定类的问题。

示例 2:覆盖 Equals 和 GetHashCode

public class EquatableByValuesMixin<[BindToTargetType]T> : Mixin<T>, IEquatable<T> where T : class
    {
        private static readonly FieldInfo[] m_TargetFields = typeof(T).GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);

        bool IEquatable<T>.Equals(T other)
        {
            if (other == null)
                return false;
            if (Target.GetType() != other.GetType())
                return false;
            for (int i = 0; i < m_TargetFields.Length; i++)
            {
                object thisFieldValue = m_TargetFields[i].GetValue(Target);
                object otherFieldValue = m_TargetFields[i].GetValue(other);

                if (!Equals(thisFieldValue, otherFieldValue))
                    return false;
            }
            return true;
        }

        [OverrideTarget]
        public new bool Equals(object other)
        {
            return ((IEquatable<T>)this).Equals(other as T);
        }

        [OverrideTarget]
        public new int GetHashCode()
        {
            int i = 0;
            foreach (FieldInfo f in m_TargetFields)
                i ^= f.GetValue(Target).GetHashCode();
            return i;
        }
    }

    public class EquatableByValuesAttribute : UsesAttribute
    {
        public EquatableByValuesAttribute()
            : base(typeof(EquatableByValuesMixin<>))
        {

        }
    }

该示例是我通过重新混音实现的动手实验。您可以在那里找到更多信息。