检测是否使用反射(c)重写了方法

给定类型 Test1 ,您可以确定它是否有自己的 实施 宣言 TestMe :

typeof(Test1).GetMethod("TestMe").DeclaringType == typeof(Test1)

如果声明来自基类型,则计算结果为false。

注意,由于这是测试声明,而不是真正的实现,因此 将 如果返回真 测试1 也是抽象的 泰斯米 是抽象的,因为 测试1 会有自己的声明。如果要排除该案例,请添加 && !GetMethod("TestMe").IsAbstract

正如@ciprianbortos所指出的,接受的答案并不完整,如果按原样使用,将导致代码中出现严重的错误。

他的评论提供了神奇的解决方案 GetBaseDefinition() 但是不需要检查 DeclaringType 如果你想要一个通用的 IsOverride 检查(我认为是这个问题的重点),只是 methodInfo.GetBaseDefinition() != methodInfo .

或者,作为扩展方法提供给 MethodInfo 我认为这会起到作用:

public static class MethodInfoUtil
{
    public static bool IsOverride(this MethodInfo methodInfo)
    {
        return (methodInfo.GetBaseDefinition() != methodInfo);
    }
}

我无法得到 Ken Beckett's proposed solution 工作。我的决定是:

    public static bool IsOverride(MethodInfo m) {
        return m.GetBaseDefinition().DeclaringType != m.DeclaringType;
    }

中有个测试 the gist .

一个简单的解决方案也适用于受保护的成员和属性,如下所示:

var isDerived = typeof(Test1 ).GetMember("TestMe", 
               BindingFlags.NonPublic 
             | BindingFlags.Instance 
             | BindingFlags.DeclaredOnly).Length == 0;

这是我的回答 here ,这反过来也提到了这个问题。

在一些非平凡的情况下也能工作的方法:

public bool Overrides(MethodInfo baseMethod, Type type)
{
    if(baseMethod==null)
      throw new ArgumentNullException("baseMethod");
    if(type==null)
      throw new ArgumentNullException("type");
    if(!type.IsSubclassOf(baseMethod.ReflectedType))
        throw new ArgumentException(string.Format("Type must be subtype of {0}",baseMethod.DeclaringType));
    while(type!=baseMethod.ReflectedType)
    {
        var methods=type.GetMethods(BindingFlags.Instance|
                                    BindingFlags.DeclaredOnly|
                                    BindingFlags.Public|
                                    BindingFlags.NonPublic);
        if(methods.Any(m=>m.GetBaseDefinition()==baseMethod))
            return true;
        type=type.BaseType;
    }
    return false;
}

还有一些难看的测试:

public bool OverridesObjectEquals(Type type)
{
    var baseMethod=typeof(object).GetMethod("Equals", new Type[]{typeof(object)});
    return Overrides(baseMethod,type);
}

void Main()
{
    (OverridesObjectEquals(typeof(List<int>))==false).Dump();
    (OverridesObjectEquals(typeof(string))==true).Dump();
    (OverridesObjectEquals(typeof(Hider))==false).Dump();
    (OverridesObjectEquals(typeof(HiderOverrider))==false).Dump();
    (OverridesObjectEquals(typeof(Overrider))==true).Dump();
    (OverridesObjectEquals(typeof(OverriderHider))==true).Dump();
    (OverridesObjectEquals(typeof(OverriderNothing))==true).Dump();
}

class Hider
{
  public virtual new bool Equals(object o)
    {
      throw new NotSupportedException();
    }
}


class HiderOverrider:Hider
{
  public override bool Equals(object o)
    {
      throw new NotSupportedException();
    }
}

class Overrider
{
  public override bool Equals(object o)
    {
      throw new NotSupportedException();
    }
}


class OverriderHider:Overrider
{
  public new bool Equals(object o)
    {
      throw new NotSupportedException();
    }
}

class OverriderNothing:Overrider
{

}

根据 this answer 还可以有一种简单的方法来检查是否重写了虚方法,而不必使用 MethodAttributes.NewSlot 属性:

public static bool HasOverride(this MethodInfo method)
{
    return (method.Attributes & MethodAttributes.Virtual) != 0 &&
           (method.Attributes & MethodAttributes.NewSlot) == 0;
}

以及另一种扩展方法

private const BindingFlags Flags = BindingFlags.NonPublic |
    BindingFlags.Public | BindingFlags.Instance;

public static bool HasOverride(this Type type, string name, params Type[] argTypes)
{
    MethodInfo method = type.GetMethod(name, Flags, null, CallingConventions.HasThis,
        argTypes, new ParameterModifier[0]);
    return method != null && method.HasOverride();
}

你可以打电话

bool hasOverride = GetType().HasOverride(nameof(MyMethod), typeof(Param1Type),
    typeof(Param2Type), ...);

检查是否 MyMethod 在派生类中重写。

就我所测试的而言,它似乎工作得很好(在我的机器上)。

有一种更好、更安全、更快的方法。 如果类实例的使用寿命很长,并且必须多次执行isoverriden检查,则此技术是有意义的。

为了解决这个问题,我们可以使用缓存和C委托,比反射快得多!

// Author: Salvatore Previti - 2011.

/// <summary>We need a delegate type to our method to make this technique works.</summary>
delegate int MyMethodDelegate(string parameter);

/// <summary>An enum used to mark cache status for IsOverridden.</summary>
enum OverriddenCacheStatus
{
    Unknown,
    NotOverridden,
    Overridden
}

public class MyClassBase
{
    /// <summary>Cache for IsMyMethodOverridden.</summary>
    private volatile OverriddenCacheStatus pMyMethodOverridden;

    public MyClassBase()
    {
        // Look mom, no overhead in the constructor!
    }

    /// <summary>
    /// Returns true if method MyMethod is overridden; False if not.
    /// We have an overhead the first time this function is called, but the
    /// overhead is a lot less than using reflection alone. After the first time
    /// this function is called, the operation is really fast! Yeah!
    /// This technique works better if IsMyMethodOverridden() should
    /// be called several times on the same object.
    /// </summary>
    public bool IsMyMethodOverridden()
    {
        OverriddenCacheStatus v = this.pMyMethodOverridden;
        switch (v)
        {
            case OverriddenCacheStatus.NotOverridden:
                return false; // Value is cached! Faaast!

            case OverriddenCacheStatus.Overridden:
                return true; // Value is cached! Faaast!
        }

        // We must rebuild cache.
        // We use a delegate: also if this operation allocates a temporary object
        // it is a lot faster than using reflection!

        // Due to "limitations" in C# compiler, we need the type of the delegate!
        MyMethodDelegate md = this.MyMethod;

        if (md.Method.DeclaringType == typeof(MyClassBase))
        {
            this.pMyMethodOverridden = OverriddenCacheStatus.NotOverridden;
            return false;
        }

        this.pMyMethodOverridden = OverriddenCacheStatus.Overridden;
        return true;
    }

    /// <summary>Our overridable method. Can be any kind of visibility.</summary>
    protected virtual int MyMethod(string parameter)
    {
        // Default implementation
        return 1980;
    }

    /// <summary>Demo function that calls our method and print some stuff.</summary>
    public void DemoMethod()
    {
        Console.WriteLine(this.GetType().Name + " result:" + this.MyMethod("x") + " overridden:" + this.IsMyMethodOverridden());
    }
}

public class ClassSecond :
    MyClassBase
{
}

public class COverridden :
    MyClassBase
{
    protected override int MyMethod(string parameter)
    {
        return 2011;
    }
}

class Program
{
    static void Main(string[] args)
    {
        MyClassBase a = new MyClassBase();
        a.DemoMethod();

        a = new ClassSecond();
        a.DemoMethod();

        a = new COverridden();
        a.DemoMethod();

        Console.ReadLine();
    }
}

当您将此程序作为控制台应用程序运行时,它将打印:

MyClassBase result:1980 overridden:False
ClassSecond result:1980 overridden:False
COverridden result:2011 overridden:True

使用Visual Studio 2010,C 4.0进行测试。 应该也适用于以前的版本,但在C小于3.0的版本上,由于对新版本中的代理进行了优化,因此速度可能会慢一些,对此的测试将不胜感激:) 但是,它仍然比使用反射更快!