Question

Customer customerOne = new Customer("John", "Doe");
Customer customerTwo = new Customer("Super", "Man");
Customer customerThree = new Customer("Crazy", "Guy");
Customer customerFour = new Customer("Jane", "Doe");
Customer customerFive = new Customer("Bat", "Man");

List<Customer> customers = new List<Customer>();
customers.Add(customerOne);
customers.Add(customerTwo);
customers.Add(customerThree);
customers.Add(customerFour);
customers.Add(customerFive);

对于具有相同姓氏的所有客户，哪些LINQ查询会返回可枚举的内容？

结果应该包括一个例子：John Doe，Jane Doe，Super Man和Bat Man

Answer 1

 customers.GroupBy(c => c.LastName).Where(g => g.Skip(1).Any()).SelectMany(c => c)

或使用LINQ语法：

        var q = from c in customers
                group c by c.LastName into g
                where g.Skip(1).Any()
                from c in g
                select c;

Answer 2

    var result = from c in customers
                 join c2 in customers on c.LastName equals c2.LastName
                 where c != c2
                 select c;

Answer 3

var groups = customers.GroupBy(c => c.LastName).Where(g => g.Skip(1).Any());
foreach(var group in groups) {
    Console.WriteLine(group.Key);
    foreach(var customer in group) {
        Console.WriteLine("\t" + customer.FirstName);
    }
}

输出：

Doe
        John
        Jane
Man
        Super
        Bat

您可以使用

将生成的组序列展平为一个序列

var list = groups.SelectMany(g => g);

如何使用LINQ查找特定属性的副本？

3 个答案: