Lambda委托解决方案

Question

我正在深入阅读Jon Skeet的C#第二版,我想到了以下问题:

怎么样能够之间进行选择的编译器list.Sort(Comparison<T>),并list.Sort(MyComparison<T>)在下面的例子:

// MyComparison has the same signature as Comparison<in T>
public delegate int MyComparison<in T>(T x, T y);

public class MyList<T> : List<T>
{
    // Sort is like Sort(Comparison<T>) except it takes a MyComparison<T> in parameter
    public int Sort(MyComparison<T> comparison)
    {
        Console.WriteLine("Sort MyComparison<T>");
        return -1;
    }
}

MyList<Product> list = new MyList<Product>();

list.Sort((product1, product2) => product1.Name.CompareTo(product2.Name));

// Equivalent to
list.Sort(new MyComparison<Product>((product1, product2) => product1.Name.CompareTo(product2.Name)));

// But not equivalent to...
list.Sort(new Comparison<Product>((product1, product2) => product1.Name.CompareTo(product2.Name)));

提前致谢

Answer 1

它选择那个,因为它在子类中并且更喜欢那些.

例如:

public class MyList<T> : List<T>
{
    public int Sort2(MyComparison<T> comparison)
    {
    }
    public int Sort2(Comparison<T> comparison)
    {
    }
}

在这种情况下,它不再理解了:

list.Sort2((product1, product2) => product1.Name.CompareTo(product2.Name));

而且你得到一个"呼叫是暧昧的"错误.