如何使用LINQ查找特定属性的副本？

2wnc66cl 于 2023-09-28 发布在其他

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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);

什么LINQ查询将返回一个枚举的所有客户具有相同的姓氏？
结果应包括以下一个示例：无名氏、无名氏、超人和 bat 侠

linq

来源：https://stackoverflow.com/questions/4250241/how-do-you-use-linq-to-find-the-duplicate-of-a-specific-property

4条答案

按热度按时间

w8rqjzmb1#

重新配制：您希望按姓氏对客户列表进行分组，筛选出具有多个元素的组，然后选择每个组的每个示例。你几乎可以把这句话逐字翻译成C#：

customers
    .GroupBy(customer => customer.LastName)
    .Where(sameLastName => sameLastName.Skip(1).Any())
    .SelectMany(customer => customer)

或者使用LINQ语法：

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

赞(0）回复(0）举报 2023-09-28

nwlqm0z12#

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

赞(0）回复(0）举报 2023-09-28

llmtgqce3#

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);
    }
}

输出量：

Doe
        John
        Jane
Man
        Super
        Bat

您可以使用以下命令将生成的组序列展平为一个序列

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

赞(0）回复(0）举报 2023-09-28

lnvxswe24#

如果你只是想找到是否有重复，你可以使用这个技巧。

var result = customers.GroupBy(c => c.Id).Count() != customers.Count();

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如何使用LINQ查找特定属性的副本？

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