C#：根据公共标识符合并两个对象？

Question

我有一个 POCO class，其中嵌套 classes 定义如下：

class Company 
{  
   string CompanyName { get; set; }
   List<Server> Servers { get; set; }
}

class Server 
{
   int ServerId { get; set;}
   string ServerName { get; set; }
   List<User> Users { get; set; }
}

class User
{
   string FirstName { get; set; }
   string LastName { get; set; }
}

假设我用以下数据实例化了它：

CompanyName = "Company A";
Servers =    
   ServerId = 134;
   ServerName = HOST01;
   Users =
      FirstName = "John";
      LastName = "Smith";
      FirstName = "Bob";
      LastName = "Jones";

   ServerId = 232;
   ServerName = HOST31;
   Users = 
      FirstName = "Michael";
      LastName = "Stevens";

   ServerId = 134;
   ServerName = HOST01;
   Users =
      FirstName = "Larry";
      LastName = "Edwards";
      FirstName = "Craig";
      LastName = "White";

我如何根据匹配 "ServerId" 属性将所有用户合并在一起？基本上，我怎么能把它变成这个？

CompanyName = "Company A";
Servers =    
   ServerId = 134;
   ServerName = HOST01;
   Users =
      FirstName = "John";
      LastName = "Smith";
      FirstName = "Bob";
      LastName = "Jones";
      FirstName = "Larry";
      LastName = "Edwards";
      FirstName = "Craig";
      LastName = "White"; 

   ServerId = 232;
   ServerName = HOST31;
   Users = 
      FirstName = "Michael";
      LastName = "Stevens";

Answer 1

使用 LINQ GroupBy 在 ServerId 上分组，并假设具有相同 ID 的服务器也具有相同的名称。

var grouped = Companies // IEnumerable<Company>
    .Select(c => new Company
    {
        CompanyName = c.CompanyName,
        Servers = c.Servers
            .GroupBy(s => s.ServerId)
            .Select(grp => new Server
            {
                ServerId = grp.Key,
                ServerName = grp.First().ServerName,
                Users = grp.SelectMany(s => s.Users)).ToList()
            })
    });

Answer 2

你可以使用Linq，像下面的代码：

1 - 通过 ID 和名称获取不同的服务器：

List<Server> distinctServers = company.Servers
    .GroupBy(s => new { s.ServerId, s.ServerName })
    .Select(s => new Server
    {
        ServerId = s.Key.ServerId,
        ServerName = s.Key.ServerName,
        Users = s.SelectMany(x => x.Users).ToList()
    }).ToList();

2 - 建立新公司或使用旧公司：

Company result = new Company
{
    CompanyName = company.CompanyName,
    Servers = distinctServers
};
// or   
company.Servers = distinctServers;

如果您有公司列表，您可以在 select 函数中使用相同的代码：

List<Company> companies = new List<Company> { company };
List<Company> companiesWithDistinctServers = companies
    .Select(c => new Company
    {
        CompanyName = c.CompanyName,
        Servers = c.Servers.GroupBy(s => new { s.ServerId, s.ServerName })
            .Select(s => new Server
            {
                ServerId = s.Key.ServerId,
                ServerName = s.Key.ServerName,
                Users = s.SelectMany(x => x.Users).ToList()
            }).ToList()
    }).ToList();

希望对您有所帮助

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