在列表中显示重复项的问题

Posted 2021-05-06

请问这是我在这里的第一篇文章，我是ASP MVC 5的新手。我已经在这个问题上工作了2天，但我不能找到解决方案。我试图将一些值分配给列表，创建一个viewmodel，然后将ViewModel中的值传递给控制器​​中的View。

问题是它完全显示列表，但它只显示列表中的最后一项（Tirus Peters）六次，而不是显示列表中的其他项目。我不知道我做错了什么。

这些是我的代码：

该模型：

namespace Learning.Models
{
    public class Employee
    {
        public int EmployeeID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public double Salary { get; set; }

        public Employee(int eID, string first, string Last, double sal)
        {
            this.EmployeeID = eID;
            this.FirstName = first;
            this.LastName = Last;
            this.Salary = sal;
        }
    }
}

ViewModel：

namespace Learning.ViewModel
{
    public class EmloyeeViewModel
    {
        public int EmployeeID { get; set; }
        public string FullName { get; set; }                
        public string Salary { get; set; }
        public string salcolor { get; set; }
    }
}

指数控制器：

public class EmployeeController : Controller
    {
        // GET: Employee
        public ActionResult Index()
        {
            EmloyeeViewModel em = new EmloyeeViewModel();
            List<EmloyeeViewModel> emVM = new List<EmloyeeViewModel>();
            List<Employee> emp = new List<Employee>()
            {
             new Employee(1, "Tony", "Cruise", 231.89),
             new Employee(2, "Bill", "George", 152.11),
             new Employee(3, "John", "Bill", 7651.29),
             new Employee(4, "Donald", "Kay", 1500.08),
             new Employee(5, "Smith", "Bill", 28.91),
             new Employee(6, "Tirus", "Peter", 1128.91)

             };

            foreach (Employee f in emp)
            {
                em.EmployeeID = f.EmployeeID;
                em.FullName = f.FirstName + " " + f.LastName;
                em.Salary = f.Salary.ToString("C");
                if (f.Salary > 100)
                {
                  em.salcolor = "green";
                }else
                {
                  em.salcolor = "red";
                }
                emVM.Add(em);

            }

            return View(emVM);
    }
}

索引视图：

@using Learning.ViewModel
    @model IList<EmloyeeViewModel>

    <h2>Got It!!</h2>

    <table>

        <tr><th>Employee ID</th><th>Full Name</th><th>Salary</th></tr>

     @foreach (var a in Model)
        {
        <tr>
            <td>@a.EmployeeID</td>
            <td>@a.FullName</td>
            <td><span style="background-color:@a.salcolor">@a.Salary</span></td>
        </tr>
        }
    </table>

答案

插入EmployeeViewModel对象时，由于只在foreach循环外部构造了一个对象，因此一次又一次地插入具有相同引用的相同对象。因此，您的列表将包含所有项目将具有相同的值在foreach循环中迭代的最后一项，因为它们共享相同的参考foreach循环实际上在同一对象上应用新值，这基本上是List中的所有项目

public class EmployeeController : Controller
    {
        // GET: Employee
        public ActionResult Index()
        {

            List<EmloyeeViewModel> emVM = new List<EmloyeeViewModel>();
            List<Employee> emp = new List<Employee>()
            {
             new Employee(1, "Tony", "Cruise", 231.89),
             new Employee(2, "Bill", "George", 152.11),
             new Employee(3, "John", "Bill", 7651.29),
             new Employee(4, "Donald", "Kay", 1500.08),
             new Employee(5, "Smith", "Bill", 28.91),
             new Employee(6, "Tirus", "Peter", 1128.91)

             };

            foreach (Employee f in emp)
            {
                EmloyeeViewModel em = new EmloyeeViewModel();
                em.EmployeeID = f.EmployeeID;
                em.FullName = f.FirstName + " " + f.LastName;
                em.Salary = f.Salary.ToString("C");
                if (f.Salary > 100)
                {
                    em.salcolor = "green";
                }
                else
                {
                    em.salcolor = "red";
                }
                emVM.Add(em);

            }

            return View(emVM);
        }
    }

另一答案

问题是您将相同的对象添加到列表中6次。您需要在每次迭代时创建一个EmployeeViewModel的新实例。见下面的代码。

foreach (Employee f in emp)
{
    // Create a new instance for each item.
    em = new EmployeeViewModel();

    em.EmployeeID = f.EmployeeID;
    em.FullName = f.FirstName + " " + f.LastName;
    em.Salary = f.Salary.ToString("C");
    if (f.Salary > 100)
    {
        em.salcolor = "green";
    }
    else
    {
        em.salcolor = "red";
    }
    emVM.Add(em);
}