Question

可能重复：
How to Count Duplicates in List with LINQ

任何想法你如何计算linq中的副本。假设我有一个Student对象列表在哪里我想找到称为'约翰'的学生数量？

Answer 1

您可以使用GroupBy：

var students = new List<string>{"John", "Mary", "John"};

foreach (var student in students.GroupBy(x => x))
{
    Console.WriteLine("{0}: {1}", student.Key, student.Count());
}

返回：

John: 2
Mary: 1

你也可以展示那些有重复的东西：

var dups = students.GroupBy(x => x)
                   .Where(g => g.Count() > 1)
                   .Select(g => g.Key);

foreach (var student in dups)
{
    Console.WriteLine("Duplicate: {0}", student);
}

返回：

Duplicate: John

注意：您需要更改GroupBy(x => x)，具体取决于您的Student对象当然是什么。在这种情况下，它只是一个string。

Answer 2

var students = new List<string> { "John", "Mary", "John" };
var duplicates = students.GroupBy(x => x)
                         .Select(x => new { Name = x.Key, Count = x.Count() });

如何计算linq中的重复数？

2 个答案: