列表项没有传递到视图

Question

因为我已经创建了一个模式叫公司，包括公司基本信息&还销售代表从不同的业务合作伙伴名单我小的web应用程序项目。这是我的联系型号：

public class Company 
    { 
     public int ID { get; set; } 
     public string Name { get; set; } 
     public string Promo { get; set; } // Yes or No field 
     public List<Contact> Contacts { get; set; } 
     public class Contact 
     { 
      [Key] 
      public int ContactID { get; set; } 
      public int CompanyID { get; set; } 
      public string ContactName { get; set; } 
      public string ContactNumber { get; set; } 
     } 
    } 

这是我如何将数据传递到我的本地数据库：

var companiesData = new Company[] 
     { 
      new Company 
      { 
      Name = "Some name", Promo="Y", Contacts = new List<Contact> { new Contact {ContactName="John Doe", ContactNumber="(828)292-2912", CompanyID=1}, 
      }}, // ... some more contacts 
     }; 
     foreach (Company c in companiesData) 
     { 
      context.Companies.Add(c); 
     } 
     context.SaveChanges(); 

如何加载联系人列表中的项目到剃刀看法？我在看我的数据库，它显示“联系人”的空白字段。其余的数据显示出来很好。

Answer 1

所以根据您的描述，这听起来像您收到的模型 - 但联系人集合为null或空。

这是因为EntityFrameworkCore需要孩子套在你的背景DB中设置使用Include被明确列入。 See here for more information

下面的代码是如何在您的模型预先加载

public class CompanyController : Controller 
{ 
    // This import is needed for using the 'Include' method. 
    using Microsoft.EntityFrameworkCore; 

    private ApplicationDbContext _context; 
    public CompanyController(ApplicationDbContext context) 
    { 
     _context = context; 
    } 
    // GET: /<controller>/ 
    public IActionResult Index() 
    { 
     List<Company> viewModelData = _context.Companies.Include(p => p.Contacts).ToList(); 

     return View(viewModelData); 
    } 
} 

public class Company 
{ 
    public int ID { get; set; } 
    public string Name { get; set; } 
    public string Promo { get; set; } // Yes or No field 
    public List<Contact> Contacts { get; set; } 
    public class Contact 
    { 
     [Key] 
     public int ContactID { get; set; } 
     public int CompanyID { get; set; } 
     public string ContactName { get; set; } 
     public string ContactNumber { get; set; } 
    } 
} 

，并且数据库上下文

public class ApplicationDbContext : IdentityDbContext<ApplicationUser> 
{ 
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) 
     : base(options) 
    { 
    } 

    protected override void OnModelCreating(ModelBuilder builder) 
    { 
     base.OnModelCreating(builder); 
     // Customize the ASP.NET Identity model and override the defaults if needed. 
     // For example, you can rename the ASP.NET Identity table names and more. 
     // Add your customizations after calling base.OnModelCreating(builder); 
    } 

    public DbSet<Company> Companies { get; set; } 
    public DbSet<Contact> Contacts { get; set; } 
} 

查看文件子集应设置模型，像这样

为例

@model List<Company> 

<h3>Do something with 'Model' here</h3> 

Answer 2

看到https://dotnetfiddle.net/xb3g68

实体：

public class Company 
{ 
    [Key] 
    public int ID { get; set; } 
    public string Name { get; set; } 
    public string Promo { get; set; } 
    public virtual List<Contact> Contacts { get; set; }  
} 

public class Contact 
{ 
    [Key] 
    public int ContactID { get; set; } 
    [ForeignKey("Company")] 
    public int CompanyID { get; set; } 
    public virtual Company Company { get; set; } 
    public string ContactName { get; set; } 
    public string ContactNumber { get; set; } 
} 

测试工具：

public static void Main() 
{ 
    Console.WriteLine("Hello World"); 
    FakeDbContext context = new FakeDbContext(); 
    var companiesData = new Company[] 
    { 
     new Company 
     { 
      Name = "Some name", Promo="Y", Contacts = new List<Contact> { new Contact {ContactName="John Doe", ContactNumber="(828)292-2912", CompanyID=1}}, 
     }, 
     new Company 
     { 
      Name = "Another name", Promo="N", Contacts = new List<Contact> { new Contact {ContactName="Jane Doe", ContactNumber="(828)292-2912", CompanyID=2}}, 
     }, 
    }; 
    foreach (Company c in companiesData) 
    { 
     context.Companies.Add(c); 
     foreach (Contact contact in c.Contacts) 
     { 
      context.Contacts.Add(contact); 
     } 
    } 
    context.SaveChanges(); 
    Console.WriteLine("Save done."); 
    var companies = context.Companies.ToList(); 
    Console.WriteLine("companies.Count: " + companies.Count); 
    for (int i = 0; i < companies.Count; i++) 
    { 
     Console.WriteLine(string.Format("company[{0}].Name: {1}", i,  companies[i].Name)); 
     for (int j = 0; j < companies[i].Contacts.Count; j++) 
     {    
Console.WriteLine(string.Format("company[{0}].Contacts[{1}].ContactName: {2}", i, j, companies[i].Contacts[j].ContactName)); 
     } 
    } 
    Console.WriteLine("Bye World"); 
} 

输出：

的Hello World

保存完成。

companies.Count：2

公司[0]请将.Name：有些名字

公司[0] .Contacts [0] .ContactName：李四

company [1] .Name：另一个名字

公司[1] .Contacts [0] .ContactName：李四

再见世界

Answer 3

你好我的最后一个项目，我做了同样的与视图模型，因为是两个不同表中的数据，并给予更多的自由要改变认为在future.So我创造出一个视图模型

public class ViewModelContactCompany 
{ 
    public String Name { get; set; } 
    List<Contact> contacts { get; set; } 
    //etc just a sample 
} 

控制器

public class Controler 
{ 
//param id is a id from company 
//to do a relationship 
public Action ControlerDetailsContact(int? id) 
{ 
    ViewModelContactCompany x = new ViewModelContactCompany(); 
    //Do a linq, sqlquery,etc 

    x.Name = "sample"; //get name of company by id; 

    for (;;) 
    { 
     //where id = contact.CompanyID 
     //add a new object typeof contact to the viewmodel 
     //with the data get from the relationship 
     x.contacts.Add(new Contact()); 
    } 

    //and in the final return object viewmodel to the view 
    return View(x); 
} 

}

现在查看

@model /patch.ViewModelContactCompany 

and here you get the data on the object return on the controler 

What is ViewModel in MVC?