LINQ - 如何连接分组依据中的两个字段？

Question

我有一个 ReportStatusEntity class，如下所示：

public class ReportsStatusEntity
{
    public string PolicyNumber { get; set; }
    public string ClientName { get; set; }
    public bool HasIndividualBrokers { get; set; }
}

假设我有以下List<ReportStatusEntity>() ：

{PolicyNumber = 1, ClientName = "John Doe", HasIndividualBrokers = True},
{PolicyNumber = 1, ClientName = "Sarah Doe", HasIndividualBrokers = True},
{PolicyNumber = 2, ClientName = "Paul Smith", HasIndividualBrokers = False},
{PolicyNumber = 3, ClientName = "Ryan Johnson", HasIndividualBrokers = False}

我想按 PolicyNumber 分组，然后将具有相同 PolicyNumber 的 ClientNames 与“&”连接起来。

分组应该是这样的：

{PolicyNumber = 1, ReportStatusEntity = (PolicyNumber = 1, ClientName = "John Doe & Sarah Doe", HasIndividualBrokers = True)},
{PolicyNumber = 2, ReportStatusEntity = (PolicyNumber = 2, ClientName = "Paul Smith", HasIndividualBrokers = False)},
{PolicyNumber = 3, ReportStatusEntity = (PolicyNumber = 3, ClientName = "Ryan Johnson", HasIndividualBrokers = False)}

如何使用 LINQ 在 C# 中完成此操作？ 谢谢你。

Answer 1

var list = new List<ReportsStatusEntity>()
{
    new ReportsStatusEntity{PolicyNumber = "1", ClientName = "John Doe", HasIndividualBrokers = true},
    new ReportsStatusEntity{PolicyNumber = "1", ClientName = "Sarah Doe", HasIndividualBrokers = true},
    new ReportsStatusEntity{PolicyNumber = "2", ClientName = "Paul Smith", HasIndividualBrokers = false},
    new ReportsStatusEntity{PolicyNumber = "3", ClientName = "Ryan Johnson", HasIndividualBrokers = false}
};

var results = list.GroupBy(r => r.PolicyNumber)
    .Select(g => new
    {
        PolicyNumber = g.Key,
        // string.Join will not work if its against a database with sql
        ClientNames = string.Join(" & ", g.Select(r => r.ClientName)),
    });

foreach (var result in results)
{
    Console.WriteLine($"Policy {result.PolicyNumber}: {result.ClientNames}");
}

// -- Outputs --
// Policy 1: John Doe & Sarah Doe
// Policy 2: Paul Smith
// Policy 3: Ryan Johnson

Answer 2

您可以先按 PolicyNumber 对所有 ReportStatusEntity 进行分组

List<List<ReportStatusEntity>> listReportStatusEntityGroupped = this.yourList.GroupBy(u => new { u.PolicyNumber,u.HasIndividualBrokers })
                                                .Select(grp => grp.ToList())
                                                .ToList();

new { u.PolicyNumber }不是强制性的，因为您只对一个参数进行分组，但您可以添加其他参数。

然后，一旦你有了List<List<ReportStatusEntity>> ，你就可以创建一个 foreach：

List<ReportStatusEntity> outputList=new List<ReportStatusEntity>();
foreach(List<ReportStatusEntity> listReportInGroup in listReportStatusEntityGroupped)
{
    ReportStatusEntity newReport = new ReportStatusEntity
    {
        PolicyNumber=listReportInGroup[0].PolicyNumber,
        HasIndividualBrokers = listReportInGroup[0].HasIndividualBrokers,
        ClientName = string.Join(" & ",listRepInGroup.Select(x=>x.ClientName)),
    };
    outputList.Add(newReport);
}

Answer 3

1- 创建一个 class 如下：

public class ReportsStatusLastEntity
{
  public int Id { get; set; }
  public string PolicyNumber { get; set; }
  public string ClientName { get; set; }
  public bool HasIndividualBrokers { get; set; }
}

2- 创建List <ReportsStatusLastEntity> liste= new List<ReportsStatusLastEntity>()

3- 通过列表 ReportStatusEntity 启动 foreach 循环

4- 检查 ReportsStatusLastEntity Id 上的 PolicyNumber。 如果为真，请添加名称。 否则添加新项目。