Question

视图模型：

Public Class UserViewModel
<Display(Name:="Roles List")> _
Public ReadOnly Property AllRoles As IEnumerable(Of SelectListItem)
    Get
        Dim dbContext As New AuthUserContext
        Dim roleQuery = (From r In dbContext.AuthRoleSet Select r Where r.isActive = True)
        Dim roles As IEnumerable(Of AuthRole) = roleQuery.ToList()
        Return roles.Select(Function(o) New SelectListItem() With {.Text = o.RoleName, .Value = o.AuthRoleID})
    End Get
End Property
Public Property User As New AuthUser
End Class

我的AuthUser课程：

Public Class AuthUser

'Properties
Public Property AuthUserID() As Integer

<Required()> _
<Display(Name:="User Name")> _
Public Property UserName() As String

<Required()> _
<Display(Name:="Current Roles")> _
Public Overridable Property AuthRoles As ICollection(Of AuthRole)

End Class

Public Class AuthRole
Public Property AuthRoleID() As Integer

<Required()> _
<Display(Name:="Role Name")> _
Public Property RoleName() As String

<Required()> _
<Display(Name:="Is Active")> _
Public Property isActive() As Boolean

Public Overridable Property AuthUser As ICollection(Of AuthUser)

End Class

我的控制器：

Function CreateUser() As ActionResult
    Dim model As New UserViewModel
    Return View(model)
End Function

我的帖子控制器：

Function CreateUser(ByVal authuser As UserViewModel) As ActionResult
    If ModelState.IsValid Then
        db.AuthUserSet.Add(authuser.User)
        db.SaveChanges()
        Return RedirectToAction("Index")
    End If

    Return View(authuser)
End Function

我的观点：

@Using Html.BeginForm()
@Html.ValidationSummary(True)
@Html.AntiForgeryToken()

@<fieldset>
    <legend>AuthUser</legend>

   <div class="editor-label">
        @Html.LabelFor(Function(model) model.User.UserName)
    </div>
    <div class="editor-field">
        @Html.TextBoxFor(Function(model) model.User.UserName)
        @Html.ValidationMessageFor(Function(model) model.User.UserName)
    </div>

    <div class="editor-label">
        @Html.LabelFor(Function(model) model.User.AuthRoles)
    </div>
    <div class="editor-field">
       @Html.DropDownListFor(Function(model) model.User.AuthRoles, Model.AllRoles, "-- Select Role--")
       @Html.ValidationMessageFor(Function(model) model.User.AuthRoles)
    </div>

    @*Have to fill this is for ModelState validation - via jQuery*@
    @Html.HiddenFor(Function(model) model.User.AuthRoles)

    <p>
        <input type="submit" value="Create" />
    </p>
</fieldset>
End Using

好吧，我在这里做的就是将我所有可用的角色都读到我的ViewModel中。我想将它们列为下拉列表，并使用从那里选择的AuthRoleID来确定在我的模型中分配哪个角色。

我的AuthRoles属性在我的帖子中总是空的。我的观点全部正确显示。

我在这里使用EF6，Code First。

Answer 1

我还不能发表评论，但我的第一个问题是DropDownList？您正在尝试将ICollection（Of AuthRole）绑定到int类型的选定值，您将只能选择一个值，而不是列表。您需要一个不同的控件，如ListBox。但是要选择一个角色：

添加属性SelectedRole ...

Public Class UserViewModel
<Display(Name:="Roles List")> _
Public ReadOnly Property AllRoles As IEnumerable(Of SelectListItem)
    Get
        Dim dbContext As New AuthUserContext
        Dim roleQuery = (From r In dbContext.AuthRoleSet Select r Where r.isActive = True)
        Dim roles As IEnumerable(Of AuthRole) = roleQuery.ToList()
        Return roles.Select(Function(o) New SelectListItem() With {.Text = o.RoleName, .Value = o.AuthRoleID})
    End Get
End Property
Public Property SelectedRole As Integer //for the drop down list to bind selected value to//
Public Property UserName As String //all you need for the view model
Public Property UserId as String //hidden value in the view when you come to edit the user and post it back to the controller
End Class

在您的视图中，将下拉列表更改为：

<div class="editor-field">
   @Html.DropDownListFor(Function(model) model.SelectedRole, Model.AllRoles, "-- Select Role--")
   @Html.ValidationMessageFor(Function(model) model.SelectedRole)
</div>

在视图中添加此隐藏字段：

  @Html.HiddenFor(Function(model) model.Id)

您的创建获取方法：

Function CreateUser() As ActionResult
    Dim model As New UserViewModel
    Return View(model)
End Function

您的编辑获取方法

Function EditUser(id as string) As ActionResult
    //logic to test if Id is empty if not fetch user from dB as variable user
    //Dim user as New AuthUser... etc
    Dim model As New UserViewModel
    model.SelectedRole = user.AuthRole // assuming one role as you are using DropDownList - you would need to use a different Editor to multi select roles and thus change the logic to get a list of roles
    model.UserName = user.UserName
    model.Id = user.Id
    Return View(model)
End Function

然后您的创建帖子控制器可以设置角色

Function CreateUser(ByVal model As UserViewModel) As ActionResult
    If ModelState.IsValid Then
        //logic to update role from authUser.SelectedRole
        Dim authuser As New AuthUser
        //update properties of authuser from the model
        authuser.UserName = model.UserName // etc.
        //
        db.AuthUserSet.Add(authuser.User)
        db.SaveChanges()
        Return RedirectToAction("Index")
    End If
//something went wrong
Return View(model)
End Function

for Edit Post方法：

Function EditUser(ByVal model As UserViewModel) As ActionResult
    If ModelState.IsValid Then
        //logic to update role from authUser.SelectedRole
        //Fetch user from the dB using the hidden field model.Id
        //update properties of fetched user from the model
        authuser.UserName = model.UserName // etc.
        //

        db.SaveChanges()
        Return RedirectToAction("Index")
    End If
//something went wrong
Return View(model)
End Function

我没有对上述内容进行测试，习惯了c＃，但希望你能得到这个想法。

根据评论对ViewModel添加进行了编辑。您可以为Create和Edit创建一个单独的视图，从而分离ViewModels - 但实质上是确保ViewModel完全不知道实体的良好实践，反之亦然

Answer 2

您的AuthRoles属性需要类型为AuthRole的对象，而您要回发Integer列表。换句话说，您无法直接发回此集合属性。相反，您需要另一个属性，例如：

Public Property SelectedAuthRoles As List(Of Integer)

然后，使用它从数据库中查找AuthRoles这些ID，最后将AuthRole添加到AuthRoles属性。

（我的VB非常缺乏，因为我几乎完全使用C＃，所以如果上面的属性不太正确，我会道歉。尽管如此，它应该足以至少传达这个想法。）

为什么我的DropDownList没有绑定到我的模型？

2 个答案: