c# - 有没有办法像 python 一样在 C# 中制作类方法？

Question

在python中，实例方法self指向类实例，就像C#中的this一样。在python中，一个类方法self指向类。是否有 C# 等效项？

这很有用，例如:

Python 示例:

class A:
  values = [1,2]

  @classmethod
  def Foo(self):
    print "Foo called in class: ", self, self.values

  @staticmethod
  def Bar():
    print "Same for all classes - there is no self"

class B(A):
  # other code specific to class B
  values = [1,2,3]
  pass

class C(A):
  # other code specific to class C
  values = [1,2,3,4,5]
  pass

A.Foo()
A.Bar()
B.Foo()
B.Bar()
C.Foo()
C.Bar()

结果:

Foo called in class:  __main__.A [1, 2]
Same for all classes - there is no self
Foo called in class:  __main__.B [1, 2, 3]
Same for all classes - there is no self
Foo called in class:  __main__.C [1, 2, 3, 4, 5]
Same for all classes - there is no self

这可能是一个很好的工具，因此类上下文中的公共(public)代码(没有实例)可以提供由子类定义的自定义行为(不需要子类的实例)。

在我看来，C# 静态方法与 python 静态方法完全一样，因为无法访问实际使用哪个类来调用该方法。

但有没有办法在 C# 中执行类方法？或者至少确定哪个类调用了方法，例如:

public class A
{
  public static List<int> values;

  public static Foo()
  {
    Console.WriteLine("How can I figure out which class called this method?");
  }
}

public class B : A
{
}

public class C : A
{
}

public class Program
{
  public static void Main()
  {
    A.Foo();
    B.Foo();
    C.Foo();
  }
}

Answer 1

使用常规静态方法无法做到这一点。可能的替代方案包括:

1) 虚拟的、重写的实例方法:

public class A
{
    public virtual void Foo()
    {
        Console.WriteLine("Called from A");
    }
}

public class B : A
{
    public override void Foo()
    {
        Console.WriteLine("Called from B");
    }
}

2)扩展方法:

public class A
{
}

public class B : A
{
}

public static class Extensions
{
    /// Allows you to do:
    /// var whoop = new B();
    /// whoop.Foo();
    public static void Foo<T>(this T thing) where T : A
    {
        Console.WriteLine("Called from " + thing.GetType().Name);
    }
}

3) 假设 A 和 B 有一个默认的构造函数:

public static class Cached<T> where T : class, new()
{
    private static T _cachedInstance;

    public static T Instance
    {
        get { return _cachedInstance ?? (_cachedInstance = new T()); }
    }
}

public static class Extensions
{
    public static void Example()
    {
        Cached<B>.Instance.Foo();
    }

    public static void Foo<T>(this T thing) where T : A, new()
    {
        Console.WriteLine("Called from " + typeof(T).Name);
    }
}