Question

我想使用distinct来删除LIST中重复的行。

这是结果集（如您所见，重复索引12和14）

id  idIndice    idName         idTipo   tamanho     caminho
12  11          Processo       3        10          C:\Program Files\Empenho\Senha.txt
13  13          Endereço       1        250         C:\Program Files\Empenho\Senha.txt
14  12          Número         2        5           C:\Program Files\Empenho\Senha.txt
15  9           Cep            5        8           C:\Program Files\Empenho\Senha.txt 
16  10          Dt. de Nasc.   4        0           C:\Program Files\Empenho\Senha.txt
12  11          Processo       3        10          C:\Program Files\Empenho\Senha.txt
14  12          Número         2        5           C:\Program Files\Empenho\Senha.txt

这是我想要的 sql （这样做）

select DISTINCT u.id, u.idIndice, t.idName, t.idTipo, t.tamanho, l.caminho
from  tgpwebged.dbo.sistema_Indexacao as u
join  tgpwebged.dbo.sistema_Indexes as t on u.idIndice = t.id
join  tgpwebged.dbo.sistema_Documentos as l on u.idDocumento = l.id
join  tgpwebged.dbo.sistema_DocType_Index as v on t.id = v.indexId
where u.idDocumento = 10

这是 LINQ 我正在尝试改编

var docObj = from u in context.sistema_Indexacao
join t in context.sistema_Indexes on u.idIndice equals t.id
join l in context.sistema_Documentos on u.idDocumento equals l.id
join v in context.sistema_DocType_Index on t.id equals v.indexId
join m in context.sistema_DocType on v.docTypeId equals m.id
where u.idDocumento == id
select new Gedi.Models.OperacoesModel.getDocIndex
{ ...  };

这就是我的尝试：

List<Gedi.Models.OperacoesModel.getDocIndex> docIndexModelDup = docObj.ToList();
List<Gedi.Models.OperacoesModel.getDocIndex> docIndexModel =
docIndexModelDup.Distinct().ToList();

但我仍然得到相同的7行，好像根本没有DISTINCT。

为什么？

Answer 1

var docIndexModel = docIndexModelDup
    .GroupBy(x => x.Id)
    .Select(g => g.First());

Answer 2

尝试：

var distinctRowsById = docObj.Select(i => i.Id)
    .Distinct()
    .Select(i => docObj.First(o => o.Id == i)

Answer 3

在getDocIndex对象上，您需要实现该接口 IEquatable.这将告诉Distinct方法在进行比较时对象是否彼此相等。这是与Distinct进行比较的正确方法，它更清晰。

public class getDocIndex: IEquatable<getDocIndex> 
{
    ....
    public bool Equals(getDocIndex otherModel)
    {
        if (otherModel == null) 
            return false;
        return this.idName == otherModel.idName && this.idTipo == otherModel.idTipo
        && this.tamanho == otherModel.tamanho && this.caminho == otherModel.caminho;
    } 
}

实现此界面后，您可以继续调用distinct，它将正常工作。

Answer 4

每当使用sql时，请在.ToList（）之前使用.Distinct（）。这可能会解决问题。例如：

var ans = (from x in xyx
             where ...
             select new ...
             {
                a = ...,
                b = ...
             }).Distinct().ToList();

Answer 5

Distinct只能使用Lambda ..就像这个

var data =_CustomerCompanyRepository.GetAll().Where(p => (p.PrimaryUser == userid || p.SecondayUser == userid)).Distinct();

如果我们想删除linq查询中的重复项。使用组

 var Account = (from c in depa join u in UserManager.Users on c.Id equals u.DepartmentId
                               group c by c into g
                               select new datadto{ Id = g.Key.Id, Name = g.Key.DepatmentName }).ToArray();

区别于不使用LINQ

5 个答案: