如何在此控制器中实现 ViewModel？ MVC，EntityFramework

Question

数据库优先设计。我想在我的 Doctor Edit page 上实现一个 DoctorViewModel，这样我就可以编辑 Doctor 和他的病人之间的关系。

问题是对选定患者列表的更改未保存。

控制器代码：

Function Edit(ByVal doctor As Doctor) As ActionResult
    If ModelState.IsValid Then

        db.Entry(doctor).State = EntityState.Modified
        db.SaveChanges()
        Return RedirectToAction("Index")

    End If

    Return View(doctor)

End Function

视图模型：

Public Class DoctorViewModel

    Public Property Doctor As Doctor
    Public Property AllPatients As IEnumerable(Of SelectListItem)

    Private Property _selectedPatients As List(Of Integer)

    Public Property pSelectedPatients As List(Of Integer)
        Get
            If _selectedPatients Is Nothing Then
                _selectedPatients = Doctor.Patients.[Select](Function(m) m.PatientID).ToList()
            End If

            Return _selectedPatients
        End Get
        Set(value As List(Of Integer))
            _selectedPatients = value
        End Set
    End Property

End Class

医生型号：

Partial Public Class Doctor
    Public Property DoctorID As Integer
    Public Property Name As String
    Public Property Description As String
    Public Property DateCreated As Nullable(Of Date)
    Public Property CreatedBy As String
    Public Property IsDeleted As Nullable(Of Boolean)

    Public Overridable Property Patients As ICollection(Of Patient) = New HashSet(Of Patient)

End Class

截图：

Index page 正确显示医生及其患者。
Edit page 显示所有可用患者并突出显示所选患者。可以在此处保存对 Doctor 属性的更改，但忽略对患者选择的任何更改。没有错误。

Answer 1

这就是解决方案。

我仍然不确定它为什么起作用，即。为什么对医生字段（姓名、描述等）的更改会保存，但对患者子列表的更改不会。

Function Edit(ByVal doctorViewModel As DoctorViewModel) As ActionResult

    If ModelState.IsValid Then

        'Grab the Doctor record and his associated patient records
        Dim item = db.Entry(Of Doctor)(doctorViewModel.Doctor)
        item.State = EntityState.Modified
        item.Collection(Function(i) i.Patients).Load()

        'Create new list of selected patients
        Dim pPatients As New List(Of Patient)
        For Each i In doctorViewModel.pSelectedPatients
            pPatients.Add(db.Patients.Find(i))
        Next

        'Replace entity's patients with the new list of patients
        item.Entity.Patients = pPatients

        'Save
        db.Entry(doctorViewModel.Doctor).State = EntityState.Modified
        db.SaveChanges()

        Return RedirectToAction("Index")

    End If

    Return View(doctorViewModel)

End Function

如何在此控制器中实现 ViewModel？ MVC，EntityFramework

How do I implement a ViewModel in this controller? MVC, EntityFramework

vb.net

entity-framework

viewmodel