c# - 如何在函数中将委托(delegate)作为 参数传递

Question

public delegate bool CompareValue<in T1, in T2>(T1 val1, T2 val2);
    public static bool CompareTwoLists<T1, T2>(IEnumerable<T1> list1, IEnumerable<T2> list2, CompareValue<T1, T2> compareValue)
    {
        return list1.Select(item1 => list2.Any(item2 => compareValue(item1, item2))).All(search => search)
                && list2.Select(item2 => list1.Any(item1 => compareValue(item1, item2))).All(search => search);
    }

在上面的函数中；如何在调用“CompareTwoLists”函数时将“compareValue”作为参数传递？

Answer 1

使用与委托(delegate)匹配的 lambda 表达式:

var people = new List<Person>();
var orders = new List<Order>();

bool result = CompareTwoLists(people, orders, 
    (person, order) => person.Id == order.PersonId);

或者作为对匹配委托(delegate)的方法的引用:

static bool PersonMatchesOrder(Person person, Order order)
{
    return person.Id == order.PersonId;
}

bool result = CompareTwoLists(people, orders, PersonMatchesOrder);