来自派生类的 C# 方法作为基构造函数中的委托(delegate)

Question

为什么下面的C#不合法？是否存在适当的解决方法？

public class Base
{
    public Base(Func<double> func) { }
}

public class Derived : Base
{
    public Derived() : base(() => Method()) <-- compiler: Cannot access non-static method 'Method' in static context
    {
    }

    public double Method() { return 1.0; }
}

Answer 1

它实际上是在基本构造函数的参数中引用“this”，这是你不能做的。

如果您的委托(delegate)确实不需要访问 this(您的示例不需要)，您可以将其设为静态。您还可以使用方法组转换来简化它:

public class Base
{
    public Base(Func<double> func)
    {
        double result = func();
    }
}

public class Derived : Base
{
    public Derived() : base(Method)
    {
    }

    public static double Method() { return 1.0; }
}

如果您确实需要使用“this”，您可以:

• 让它成为一个虚方法而不是调用委托(delegate)

• 让它成为一个静态方法，接受一个适当的实例，例如

  public class Base
  {
      public Base(Func<Base, double> func)
      {
          double result = func(this);
      }
  }
  
  public class Derived : Base
  {
      public Derived() : base(x => Method(x))
      {
      }
  
      private static double Method(Base b) 
      {
          // The documentation would state that the method would only be called
          // from Base using "this" as the first argument
          Derived d = (Derived) b;
      }
  }