如何解决与 LinQ 的多个联接？

Question

所以，假设我有一个Contest，它可以有多个ContestCulture。 对于本次比赛，我必须拥有 Documents ，其中有 DocumentType 和 Culture（规则、条款和条件、隐私政策）

对于每个ContestCulture，我必须为每个DocumentType 至少有一个Document，以便Contest 有效。

假设我有一个 Contest 和 2 个 ContestCulture (fr-CA, en-CA) 我必须至少有 6 个 Document 用于那个 Contest

• 文档 1：文化 1、规则
• 文档 2：文化 1、条款和条件
• 文档 3：文化 1、隐私政策
• 文档 4：文化 2、规则
• 文档 5：文化 2、条款和条件
• 文档 6：文化 2、隐私政策

实体如下：

public class Document
{
    public DocumentType DocumentType { get; set; }
    public int CultureId { get; set; }
    public Culture Culture { get; set; }
    public int ContestId { get; set; }
    public Contest Contest { get; set; }
    //Some other properties
    //...
}

public class Contest
{
    public List<Document> Documents { get; set; }
    public List<ContestCulture> ContestCultures { get; set; }
    //Some other properties
    //...

}

public class ContestCulture 
{
     public int ContestId { get; set; }
    public Contest Contest { get; set; }

    public int CultureId { get; set; }
    public Culture Culture { get; set; }

    //Some other properties
    //...
}

public class Culture
{
    public string Code { get; set; }
    public string Name { get; set; }
}

现在已经设置了上下文..

我有 3 个列表：

• DocumentType 列表（enum 值列表）
• ContestCulture ID 列表（int 列表）
• Documents 的Contest 列表（Document 列表）

如何检查每个DocumentType 是否至少有1 个Document ContestCulture？

我对 LinQ 真的很陌生，所以我尝试了这个：

from cultureId in list_usedCultureIdsForContest
join doc in documents on cultureId equals doc.CultureId into temp1
from t in temp1.DefaultIfEmpty()
select new {cultureId, t};

但它只给我我拥有的那些，如下所示：

Answer 1

首先，从enum 获取每种文化所需的文档类型数量：

var numDocumentTypes = Enum.GetNames(typeof(DocumentType)).Length;

然后，计算每个CultureId 拥有的不同文档类型的数量：

var docTypesPerCulture = documents.GroupBy(d => d.CultureId)
                                  .Select(dg => new {
                                        CultureId = dg.Key,
                                        Count = dg.Select(d => d.DocumentType).Distinct().Count()
                                   });

现在，您可以左连接到使用的文化 ID（以处理没有文档的文化 ID）并过滤到缺少文档类型的文化 ID：

var ans = list_usedCultureIdsForContest.GroupJoin(docTypesPerCulture,
                                                  ci => ci,
                                                  dpc => dpc.CultureId,
                                                  (ci, dpcj) => dpcj.Any() ? dpcj.Select(dpc => new { CultureId = ci, Count = dpc.Count }).Single()
                                                                           : new { CultureId = ci, Count = 0 }
                                        )
                                       .Where(cic => cic.Count != numDocumentTypes);

Answer 2

简单：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication159
{
    class Program
    {

        static void Main(string[] args)
        {
            List<Document> contest = new List<Document>() {
                new Document() { contestCulture = 1,  documentType = DocumentType.Rules },
                new Document() { contestCulture = 1,  documentType = DocumentType.TermsAndConditions },
                new Document() { contestCulture = 1,  documentType = DocumentType.PrivacyPolicy },
                new Document() { contestCulture = 2,  documentType = DocumentType.Rules },
                new Document() { contestCulture = 2,  documentType = DocumentType.TermsAndConditions },
                new Document() { contestCulture = 2,  documentType = DocumentType.PrivacyPolicy  }
            };

            var valid = contest.GroupBy(x => x.contestCulture)
                .Select(x => new { culture = x.Key, valid = Valid(x.ToList()) })
                .ToList();


        }

        static bool Valid(List<Document> documents)
        {
            return documents.Any(x => x.documentType == DocumentType.Rules) &&
                documents.Any(x => x.documentType == DocumentType.TermsAndConditions) &&
                documents.Any(x => x.documentType == DocumentType.PrivacyPolicy);
        }
    }
    public enum DocumentType
    {
        Rules,
        TermsAndConditions,
        PrivacyPolicy
    }
    public class Document
    {
        public int contestCulture { get; set; }
        public DocumentType documentType { get; set; }
    }

}

---

另一种方式

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication159
{
    class Program
    {

        static void Main(string[] args)
        {
            List<Document> contest = new List<Document>() {
                new Document() { contestCulture = 1,  documentType = DocumentType.Rules },
                new Document() { contestCulture = 1,  documentType = DocumentType.TermsAndConditions },
                new Document() { contestCulture = 1,  documentType = DocumentType.PrivacyPolicy },
                new Document() { contestCulture = 2,  documentType = DocumentType.Rules },
                new Document() { contestCulture = 2,  documentType = DocumentType.TermsAndConditions },
                new Document() { contestCulture = 2,  documentType = DocumentType.PrivacyPolicy  }
            };

            var valid = contest.GroupBy(x => x.contestCulture)
                .Select(x => new { culture = x.Key, valid = Valid(x.ToList()) })
                .ToList();

        }

        static bool Valid(List<Document> documents)
        {
            int or = 0;
            foreach (Document document in documents)
            {
                or |= (int)document.documentType;
            }
            return (or == 7) ? true : false;
        }
    }
    public enum DocumentType
    {
        Rules = 1,
        TermsAndConditions = 2,
        PrivacyPolicy = 4
    }
    public class Document
    {
        public int contestCulture { get; set; }
        public DocumentType documentType { get; set; }
    }

}