Question

我有以下2个列表。 EmployeesDto List，AccountsDto List。从这两个列表中，我需要准备第三个列表：List。为简单起见，我们假设EmployeesDto具有以下结构：

Class  EmployeesDto {
    public int EmpId {get; set; }
    public string EmpName {get; set; }
}
//And the AccountsDto is like:
Class  AccountsDto {
    public int EmpId {get; set; }
    public bool IsManager {get; set; }
}
// And LinkedEmployeesDto:
Class  LinkedEmployeesDto {
    public int EmpId {get; set; }
    public string EmpName {get; set; }
    public bool IsManager {get; set; }
}

现在我需要根据以上两个列表创建List，“IsManager＆＃39;属性将从列表中设置，其中EmpId匹配列表和列表t。我可以使用foreach来做到这一点，但是通过LINQ寻找更优雅的方式。

提前致谢。

Answer 1

您可以使用linq加入，以获得第三个列表

List<EmployeesDto> lstEmployeesDto = new List<EmployeesDto>();
        List<AccountsDto> lstAccountsDto = new List<AccountsDto>();

        var result = lstEmployeesDto.Join(lstAccountsDto,
                                   e => e.EmpId,
                                   d => d.EmpId, (employee, account) => new
                                   {
                                       EmpId = employee.EmpId,
                                       EmpName = employee.EmpName,
                                       IsManager = account.IsManager
                                   });

Answer 2

如果您想避免加入，可以执行此操作。此示例假定您始终拥有相关数据以及Employees和Accounts之间的一对一关系。您可能希望添加自定义检查以确保。

List<EmployeesDto> Employees = new List<EmployeesDto>();
List<AccountsDto> Accounts = new List<AccountsDto>();

var linkedEmployees = Employees
                         .Select(e => 
                             new LinkedEmployeesDto
                                  { 
                                    EmpId = e.EmpId, 
                                    EmpName = e.EmpName,
                                    IsManager = Accounts
                                               .Single(a => a.EmpId == e.EmpId)
                                               .IsManager
                                  })
                         .ToList();

Answer 3

根据您的需要，您可以使用以下两种表达方式。

    List<EmployeesDto> employees = new List<EmployeesDto>();
    employees.Add(new EmployeesDto { EmpId = 1, EmpName = "1" });
    employees.Add(new EmployeesDto { EmpId = 2, EmpName = "2" });
    employees.Add(new EmployeesDto { EmpId = 3, EmpName = "3" });
    employees.Add(new EmployeesDto { EmpId = 4, EmpName = "4" });

    List<AccountsDto> accounts = new List<AccountsDto>();
    accounts.Add(new AccountsDto { EmpId = 1, IsManager = true });
    accounts.Add(new AccountsDto { EmpId = 2, IsManager = true });


    // To get only those records which are in accounts list
    IEnumerable<LinkedEmployeesDto> linkedEmployees = employees.Join(accounts,
                                                                     employee => employee.EmpId,
                                                                     account => account.EmpId,
                                                                     (employee, account) => new LinkedEmployeesDto
                                                                     {
                                                                         EmpId = employee.EmpId,
                                                                         EmpName = employee.EmpName,
                                                                         IsManager = account.IsManager
                                                                     });

    // To get all the records from employee and set IsManager as false if record no in accounts list
    linkedEmployees = from employee in employees
                      join account in accounts on employee.EmpId equals account.EmpId into holder
                      from acc in holder.DefaultIfEmpty()
                      select new LinkedEmployeesDto
                      {
                          EmpId = employee.EmpId,
                          EmpName = employee.EmpName,
                          IsManager = (acc == null) ? false : acc.IsManager
                      };

Answer 4

您可以使用LinQ中的Join来比较2个列表中的相等性并形成新列表。

List<EmployeesDto> Employees = new List<EmployeesDto>();            
        List<AccountsDto> Accounts = new List<AccountsDto>();           
        List<LinkedEmployeesDto> linkedEmployees = new List<LinkedEmployeesDto>();
        linkedEmployees = (from emp in Employees
                           join acc in Accounts
                                on emp.EmpId equals acc.EmpId
                           select new LinkedEmployeesDto()
                           {
                               EmpId = emp.EmpId,
                               EmpName = emp.EmpName,
                               IsManager = acc.IsManager
                           }).ToList();

如何迭代两个自定义对象列表并使用LINQ在C＃中准备第三个？

4 个答案: