将平面集合转换为一个？多个 C#/Linq

Question

我有一个数据集在这个class的集合中：

public class AOClientData
{
    public int boclient_id { get; set; }
    public string beneficialownertype_name { get; set; }
    public int account_id { get; set; }
    public string fi_name { get; set; }
    public string acct_number { get; set; }
}

看起来像这样：

boclient_id    beneficialownertype_name   account_id     fi_name      acct_number
1001           Joe                        501            ABC          12345
1001           Joe                        502            BCA          54321
1002           Fred                       990            DDd          22334

目标是将其纳入本class的集合：

   public class ClientInfo 
    {
        public int boclient_id { get; set; }
        public string beneficialownertype_name { get; set; }
        public List<AccountInfo> Accounts { get; set; }
    }

与这个class是一对多的关系：

public class AccountInfo 
{
    public int account_id { get; set; }
    public string fi_name { get; set; }
    public string acct_number { get; set; }
}

结果应该是 ClientInfo 对象的集合，如下所示：

1001     Joe    {501,           ABC,  12345         },
                {502,           BCA,  54321         }
1002     Fred   {990,         DDd,  22334      }

这是我的尝试，它确实加载了所有客户端数据，但是 ClientInfo.Accounts 属性中的 AccountInfo 对象的属性都是空的：

        List<ClientInfo> clientInfo = aoClientData
            .GroupBy(c => new { c.boclient_id, c.beneficialownertype_name })
            .Select(xGrp => new ClientInfo
            {
                boclient_id = xGrp.Key.boclient_id,
                beneficialownertype_name = xGrp.Key.beneficialownertype_name,
                Accounts = xGrp
                    .Select(c => new AccountInfo
                    {
                        account_id = c.account_id,
                        fi_name = c.fi_name,
                        acct_number = c.acct_number
                    })
                    .ToList()
            })
            .ToList();

LINQ 有什么问题？

Answer 1

您已将 c 变量重新用作 aoCLientData 项和分组项。在你的内部 select 使用 .Select(a => new AccountInfo... 然后使用 a 而不是 c 到 select a.account_id、a.fi_name 和 a.acct_number.

var result = data
    .GroupBy(x => new { x.boclient_id, x.beneficialownertype_name })
    .Select(x => 
        new ClientInfo
        {
            boclient_id = x.Key.boclient_id,
            beneficialownertype_name = x.Key.beneficialownertype_name,
            Accounts = x.Select(a =>
                new AccountInfo 
                {
                    account_id = a.account_id,
                    fi_name = a.fi_name,
                    acct_number = a.acct_number
                }).ToList()
        });

Answer 2

如果我查看您的代码，我不明白为什么您会得到多个 ClientInfos，每个属性 Accounts 的值都为 null。我什至不希望有一个空的帐户列表。

您是否尝试过使用带有参数 resultSelector 的 overload of GroupBy？

List<ClientInfo> clientInfo = aoClientData
    .GroupBy(

    // parameter keySelector:
    clientInfo => new
    {
        BoClientId = clientInfo.boclient_id,
        BeneficialOwnerTypeName = clientInfo.beneficialownertype_name,
    })

    // parameter resultSelector: for every key item with all its zero or more AOClientData
    // make one new ClientInfo
    (key, aoClientsWithThisKey) => new ClientInfo
    {
        boclient_id = key.BoClientId,
        beneficialownertype_name = key.BeneficialOwnerTypeName,
        Accounts = aoClientsWithThisKey.Select(aoClient => new AccountInfo
        {
            account_id = aoClient.account_id,
            fi_name = aoClient.fi_name,
            acct_number = aoClient.acct_number
        })
        .ToList(),
    })
    .ToList();

Answer 3

解决方法如下：

var items = aoClientData.GroupBy(c => new { c.boclient_id, c.beneficialownertype_name })
    .Select(grp => new ClientInfo()
    {
        boclient_id = grp.Key.boclient_id,
        beneficialownertype_name = grp.Key.beneficialownertype_name,                            
    Accounts = grp.Select(r => new AccountInfo() 
    { 
        account_id = r.account_id,
        acct_number = r.acct_number
    }).ToList()
}).ToList();

将平面集合转换为一个？多个 C#/Linq

Convert flat collection to one-?many C#/Linq

c#

linq

collections

visual-studio-2019