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在对象列表中查找重复的对象数据

.net c#

Chris Conway · 技术社区 · 15 年前

public Person
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int SSN { get; set; }
}

我有一份清单:

List<Person> persons = GetPersons();

List<Person> dupes

原始列表可能如下所示:

persons = new List<Person>();
persons.Add(new Person { Id = 1, 
                         FirstName = "Chris", 
                         LastName="Columbus", 
                         SSN=111223333 }); // Is a dupe
persons.Add(new Person { Id = 1, 
                         FirstName = "E.E.", 
                         LastName="Cummings", 
                         SSN=987654321 });
persons.Add(new Person { Id = 1, 
                         FirstName = "John", 
                         LastName="Steinbeck", 
                         SSN=111223333 }); // Is a dupe
persons.Add(new Person { Id = 1, 
                         FirstName = "Yogi", 
                         LastName="Berra", 
                         SSN=123456789 });

最终的结果将是卡明斯和贝拉出现在最初的人物名单中,哥伦布和斯坦贝克也将出现在被称为dupes的名单中。

非常感谢!

7 回复 | 直到 15 年前

Neil Slater 11 年前

这将获得重复的SSN:

var duplicatedSSN =
    from p in persons
    group p by p.SSN into g
    where g.Count() > 1
    select g.Key;

var duplicated = persons.FindAll( p => duplicatedSSN.Contains(p.SSN) );

然后只需在重复项上迭代并删除它们。

duplicated.ForEach( dup => persons.Remove(dup) );

Chris Conway 15 年前

var duplicatedSSN =
    from p in persons
    group p by p.SSN into g
    where g.Count() > 1
    select g.Key;

var duplicates = new List<Person>();

foreach (var dupeSSN in duplicatedSSN)
{
    foreach (var person in persons.FindAll(p => p.SSN == dupeSSN))
        duplicates.Add(person);
}

duplicates.ForEach(dup => persons.Remove(dup));

Graeme Bradbury 15 年前

List<Person> actualPersons = persons.Distinct().ToList();
List<Person> duplicatePersons = persons.Except(actualPersons).ToList();

Peter Ombwa 7 年前

基于上述@gcores的建议。

如果要将复制SSN的单个对象添加回人员列表,请添加以下行:

IEnumerable<IGrouping<string, Person>> query = duplicated.GroupBy(d => d.SSN, d => d);

        foreach (IGrouping<string, Person> duplicateGroup in query)
        {
            persons.Add(duplicateGroup .First());
        }

Steven Evers 15 年前

如果您这样实现IComparable:

int IComparable<Person>.CompareTo(Person person)
{
    return this.SSN.CompareTo(person.SSN);
}

for (Int32 i = 0; i < people.Count; i++)
{
    for (Int32 j = 1; j < items.Count; j++)
    {
        if (i != j && items[i] == items[j])
        {
            // duplicate
        }
    }
}

Mike Marshall 15 年前

Dictionary<string, int> ssnTable = new Dictionary<string, int>();

foreach (Person person in persons)
{
   try
   {
      int count = ssnTable[person.SSN];
      count++;
      ssnTable[person.SSN] = count;
   }
   catch(Exception ex)
   {
       ssnTable.Add(person.SSN, 1);
   }
}

// traverse ssnTable here and remove items where value of entry (item count) > 1

user212218 user212218 13 年前

做 persons 必须是一个 List<Person> ? 如果它是一个 Dictionary<int, Person>

var persons = new Dictionary<int, Person>();

...

// For each person you want to add to the list:
var person = new Person
{
  ...
};

if (!persons.ContainsKey(person.SSN))
{
  persons.Add(person.SSN, person);
}

// If you absolutely, positively got to have a List:
using System.Linq;
List<Person> personsList = persons.Values.ToList();

如果您使用的是 Person (与可能恰好具有相同属性的不同实例相反),使用 HashSet .