Question

利用MVC 5和实体框架我正在尝试为我的索引视图设置一个ViewModel，以显示员工及其目标。我有一个员工表，一个employeeMap表（带有效负载的连接表）和一个目标表。 Employee和EmployeeMap之间以及Goal和EmployeeMap之间存在一对多的关系。我是一个新手，并且陷入了索引视图，最初应该显示员工，当选择一名员工时，应该显示员工的目标。

我无法正确执行索引操作：

var viewModel = new EmployeeGoals（）;

        viewModel.Employees = db.Employees
            .Include(d => d.Department)
            .Include(e => e.Position)
            .Include(m => m.EmployeeMaps)
            .Where(d => d.OrganizationID == oid && d.Department.ManagerID == currentUser.EmployeeID)
            .OrderBy(d => d.HireDate);


        if (id != null)
        {
            ViewBag.EmployeeID = id.Value;
            viewModel.EmployeeMaps = viewModel.Employees.Where(e => e.ID == id.Value).Single().EmployeeMaps;
            viewModel.Goals = viewModel.EmployeeMaps.Where(e => e.EmployeeID == ViewBag.EmployeeID).Select(e => e.Goals);



            }

            if (goalID != null)
            {
                ViewBag.GoalID = goalID.Value;
                viewModel.Activities = viewModel.Goals.Where(
                    x => x.ID == goalID).Single().Activities;
            }

            return View(viewModel);

我确实正确填充了viewmodel.employees，但没有填充viewmodel.goals

哦，视图模型是：

public class EmployeeGoals
    {
        public IEnumerable<EmployeeMap> EmployeeMaps { get; set; }
        public IEnumerable<Employee> Employees { get; set; }
        public IEnumerable<Goal> Goals { get; set; }
    }

一个暗示帮助我过去这将是伟大的。感谢

使用不同的方法让它工作：

viewModel.Employees = db.Employees
                .Include(d => d.Department)
                .Include(e => e.Position)
                .Include(m => m.EmployeeMaps)
                .Where(d => d.OrganizationID == oid && d.Department.ManagerID == currentUser.EmployeeID)
                .OrderBy(d => d.HireDate);


            if (id != null)
            {
                ViewBag.EmployeeID = id.Value;
                viewModel.EmployeeMaps = viewModel.Employees.Where(e => e.ID == id.Value).Single().EmployeeMaps;
                viewModel.Goals = from g in db.Goals
                                  join m in db.EmployeeMaps on g.ID equals m.GoalID
                                  join e in db.Employees on m.EmployeeID equals e.ID 
                                  where m.EmployeeID == id.Value
                                  select g;
            }

无法弄清楚如何使用导航属性获得结果，因此最终得到了上述解决方案。它完成了这项工作，但我经常点击数据库吗？最后，结合了LINQ语法 - 应该只使用其中一个，我知道： - /

Answer 1

您应该使用SelectMany：

viewModel.Goals = viewModel.EmployeeMaps
                           .Where(e => e.EmployeeID == ViewBag.EmployeeID)
                           .SelectMany(e => e.Goals);

因为EmployeeMaps.Where()是IEnumerable，所以Select会产生IEnumerable<IEnumerable<Goal>>。 SelectMany将此展平为IEnumerable<Goal>。

如何让这个ViewModel正确？

1 个答案: