ASP.NET MVC 5 - 多对一关系的脚手架

我正在使用VS 2013开发ASP.NET MVC 5,EF 6,Razor Engine,VB语言和数据库第一种方法.

现在,在我的数据库中; 我有两个表格如下:

CREATE TABLE [dbo].[Group]
(
    [Id]    INT          NOT NULL PRIMARY KEY IDENTITY(1, 1), 
    [Name]  VARCHAR(50)  NOT NULL
)

和

CREATE TABLE [dbo].[Subscriber]
(
    [Id]          INT              NOT NULL  PRIMARY KEY IDENTITY(1, 1),
    [FirstName]   [nvarchar](100)  NOT NULL,
    [MiddleName]  [nvarchar](100)  NULL,
    [LastName]    [nvarchar](100)  NOT NULL, 
    [Email]       [varchar] (200)  NOT NULL  UNIQUE, 
    [GroupId]     INT              NULL      REFERENCES [Group] ON DELETE SET NULL
)

现在,当我使用脚手架自动生成控制器和视图时; 我Group在"创建订阅者"和"编辑订阅者"视图中得到一个控件(所有项目都在里面).

但实际上,我希望"创建组"和"编辑组"视图向我询问我Subscribers想要添加到特定组中.对于相同的HTML控制可以是复选框的列表或<选择多个="多个">与所有Subscriber的项目,如<选项>秒.

我该如何自动生成/实现它？

1 个回答

• 不要过分依赖脚手架.重点在于它为您提供了工作的基础; 对你的观点来说,这不是万能的.您可以而且应该修改脚手架以满足您的需求,老实说,通常情况下,从头开始比尝试撤消脚手架增加的所有不必要的绒毛更容易.

  也就是说,特别是在一次选择多个相关项目时,您需要一个视图模型.试图使用你的实体来快速耗尽.所以创建一个类,如:

  public class GroupViewModel
  {
      // `Group` properties you need to edit here
  
      public List<int> SelectedSubscriberIds { get; set; }
  
      public IEnumerable<SelectListItem> SubscriberChoices { get; set; }
  }
  

  然后,在你的控制器中:

  // We'll use this code multiple times so it's factored out into it's own method
  private void PopulateSubscriberChoices(GroupViewModel model)
  {
      model.SubscriberChoices = db.Subscribers.Select(m => new SelectListItem
      {
          Value = m.Id.ToString(),
          Text = m.FirstName + " " + m.LastName
      });
  }
  
  public ActionResult Create()
  {
      var model = new GroupViewModel();
  
      PopulateSubscriberChoices(model);
      return View(model);
  }
  
  [HttpPost]
  public ActionResult Create(GroupViewModel model)
  {
      if (ModelState.IsValid)
      {
          // Map the posted values onto a new `Group` instance. To set `Subscribers`,
          // lookup instances from the database using the list of ids the user chose
          var group = new Group
          {
              Name = model.Name,
              Subscribers = db.Subscribers.Where(m => model.SelectedSubscriberIds.Contains(m.Id))
          };
          db.Groups.Add(group);
          db.SaveChanges()
  
          return RedirectToAction("Index");
      }
  
      PopulateSubscriberChoices(model);
      return View(model);
  }
  
  public ActionResult Edit(int id)
  {
      var group = db.Groups.Find(id);
      if (group == null)
      {
          return new HttpNotFoundResult();
      }
  
      // Map `Group` properties to your view model
      var model = new GroupViewModel
      {
          Name = group.Name,
          SelectedSubscriberIds = group.Subscribers.Select(m => m.Id).ToList()
      };
  
      PopulateSubscriberChoices(model);
      return View(model);
  }
  
  [HttpPost]
  public ActionResult Edit(int id, GroupViewModel model)
  {
      var group = db.Groups.Find(id);
      if (group == null)
      {
          return new HttpNotFoundResult();
      }
  
      if (ModelState.IsValid)
      {
          group.Name = model.Name;
  
          // Little bit trickier here
          // First remove subscribers that are no longer selected
          group.Subscribers.Where(m => !model.SelectedSubscriberIds.Contains(m.Id))
              .ToList().ForEach(m => group.Subscribers.Remove(m));
  
          // Now add newly selected subscribers
          var existingSubscriberIds = group.Subscribers.Select(m => m.Id);
          var newSubscriberIds = model.SelectedSubscriberIds.Except(existingSubscriberIds);
          db.Subscribers.Where(m => newSubscriberIds.Contains(m.Id))
              .ToList().ForEach(m => group.Subscribers.Add(m));
  
          db.Entry(group).State = EntityState.Modified;
          db.SaveChanges()
  
          return RedirectToAction("Index");
      }
  
      PopulateSubscriberChoices(model);
      return View(model);
  }
  

  编辑后期操作是最困难的.为了不会出现有关重复键等的错误,您需要确保不要将重复项添加到集合中.您还需要确保删除此组与用户取消选择的任何项之间的关系.除此之外,它非常直接.

  最后在您的视图中,您只需要渲染选择列表:

  @model Namespace.To.GroupViewModel
  
  ...
  
  @Html.ListBoxFor(m => m.SelectedSubscriberIds, Model.SubscriberChoices)
  

  UPDATE

  添加转换的VB代码.这可能无法100%开箱即用.任何具有更多VB经验的人都可以随意编辑以纠正任何问题.

  查看模型

  Public Class GroupViewModel
      ' Group properties you need to edit here
  
      Public Property SelectedSubscriberIds As List(Of Integer)
      Public Property SubscriberChoices As IEnumerable(Of SelectListItem)
  
  End Class
  

  控制器代码

  ' We'll use this code multiple times so it's factored out into it's own method
  Private Sub PopulateSubscriberChoices(model As GroupViewModel)
      model.SubscriberChoices = db.Subscribers.[Select](Function(m) New SelectListItem With { _
          .Value = m.Id, _
          .Text = m.FirstName & " " & m.LastName _
      })
  End Sub
  
  Public Function Create() As ActionResult
      Dim model as New GroupViewModel
      PopulateSubscriberChoices(model)
      Return View(model)
  End Function
  
  <HttpPost> _
  Public Function Create(model As GroupViewModel) As ActionResult
      If ModelState.IsValid Then
          ' Map the posted values onto a new `Group` instance. To set `Subscribers`,
          ' lookup instances from the database using the list of ids the user chose
          Dim group = New Group With { _
              .Name = model.Name, _
              .Subscribers = db.Subscribers.Where(Function(m) model.SelectedSubscriberIds.Contains(m.Id)) _
          }
          db.Groups.Add(group)
          db.SaveChanges()
  
          Return RedirectToAction("Index")
      End If
  
      PopulateSubscriberChoices(model)
      Return View(model)
  End Function
  
  Public Function Edit(id As Integer) As ActionResult
      Dim group = db.Groups.Find(id)
      If group Is Nothing Then
          Return New HttpNotFoundResult()
      End If
  
      ' Map `Group` properties to your view model
      Dim model = New GroupViewModel With { _
          .Name = group.Name, _
          .SelectedSubscriberIds = group.Subscribers.[Select](Function(m) m.Id).ToList _
      }
  
      PopulateSubscriberChoices(model)
      Return View(model)
  End Function
  
  <HttpPost> _
  Public Function Edit(id As Integer, model As GroupViewModel) As ActionResult
      Dim group = db.Groups.Find(id)
      If group Is Nothing Then
          Return New HttpNotFoundResult()
      End If
  
      If ModelState.IsValid Then
          group.Name = model.Name
  
          ' Little bit trickier here
          ' First remove subscribers that are no longer selected
          group.Subscribers.Where(Function(m) Not model.SelectedSubscriberIds.Contains(m.Id)).ToList().ForEach(Function(m) group.Subscribers.Remove(m))
  
          ' Now add newly selected subscribers
          Dim existingSubscriberIds = group.Subscribers.[Select](Function(m) m.Id)
          Dim newSubscriberIds = model.SelectedSubscriberIds.Except(existingSubscriberIds)
          db.Subscribers.Where(Function(m) newSubscriberIds.Contains(m.Id)).ToList().ForEach(Function(m) group.Subscribers.Add(m))
  
          db.Entry(group).State = EntityState.Modified
          db.SaveChanges()
  
          Return RedirectToAction("Index")
      End If
  
      PopulateSubscriberChoices(model)
      Return View(model)
  End Function
  

  2022-12-11 02:07 回答

    建霖怡旭家其

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