使用 MSDN 上的示例解释：
SelectList 类 ( http://msdn.microsoft.com/en-us/library/system.web.mvc.selectlist_members(v=vs.90).aspx )
SelectListItem ( http://msdn.microsoft.com/en-us/library/system.web.mvc.multiselectlist.items(v=vs.90).aspx )
和 IEnumerable ( http://msdn.microsoft.com/en-us/library/system.collections.ienumerable(v=vs.90).aspx )
我从示例 Person/People 代码创建了以下类。
Public Class Choice
'
Private _Value As String = Nothing
Private _Text As String = Nothing
Private _Selected As Boolean = Nothing
'
Property ItemValue As String
Get
Return _Value
End Get
Set(value As String)
_Value = value
End Set
End Property
'
Property ItemText As String
Get
Return _Text
End Get
Set(value As String)
_Text = value
End Set
End Property
'
Property ItemSelected As Boolean
Get
Return _Selected
End Get
Set(value As Boolean)
_Selected = value
End Set
End Property
'
Public Sub New(ByVal pValue As String, ByVal pText As String)
Me._Value = pValue
Me._Text = pText
Me._Selected = False
End Sub
'
Public Sub New(ByVal pValue As String, ByVal pText As String, pSelected As Boolean)
Me._Value = pValue
Me._Text = pText
Me._Selected = pSelected
End Sub
'
End Class
Public Class Choices
Implements IEnumerable
'
Private _Choices() As Choice
'
Public ReadOnly Property SelectedValue() As Choice
Get
Dim i As Integer = Nothing
Dim x As Choice = Nothing
For i = 0 To _Choices.Length - 1
If _Choices(i).ItemSelected Then
x = _Choices(i)
Exit For
End If
Next i
Return x
i = Nothing
x = Nothing
End Get
End Property
'
Public Sub New(ByVal pArray() As Choice)
_Choices = New Choice(pArray.Length - 1) {}
Dim i As Integer
For i = 0 To pArray.Length - 1
_Choices(i) = pArray(i)
Next i
End Sub
'
Public Function GetEnumerator() As IEnumerator Implements IEnumerable.GetEnumerator
Return New ChoicesEnum(_Choices)
End Function
'
End Class
Public Class ChoicesEnum
Implements IEnumerator
'
Public _Choices() As Choice
'
Dim position As Integer = -1
'
Public Sub New(ByVal list() As Choice)
_Choices = list
End Sub
'
Public Function MoveNext() As Boolean Implements IEnumerator.MoveNext
position = position + 1
Return (position < _Choices.Length)
End Function
'
Public Sub Reset() Implements IEnumerator.Reset
position = -1
End Sub
'
Public ReadOnly Property Current() As Object Implements IEnumerator.Current
Get
Try
Return _Choices(position)
Catch ex As IndexOutOfRangeException
Throw New InvalidOperationException()
End Try
End Get
End Property
'
End Class
在我的模型中，我已将其声明如下
Private _Gender As Integer = Nothing
在我的控制器中，我实例化一个选择列表，如下所示：
Friend Function GetGenderList(SelId As Integer) As SelectList
'
Dim ChoicesArray() As Choice = { _
New Choice("0", "Please Select Gender", IIf(SelId = 0, True, False)), _
New Choice("1", "Male", IIf(SelId = 1, True, False)), _
New Choice("2", "Female", IIf(SelId = 2, True, False)), _
New Choice("3", "Unspecified", IIf(SelId = 3, True, False))}
Dim ChoicesList As New Choices(ChoicesArray)
GetGenderList = New SelectList(ChoicesList, ChoicesList(SelId))
ChoicesList = Nothing
ChoicesArray = Nothing
'
End Function
然后我将视图数据中的选择列表传递给视图
<ChildActionOnly()> _
Function EditPersonalUserCtrl(ByVal MyPersonal As MemberPersonalModel, FoundErrorInfo As String) As PartialViewResult
Dim sxGenderList As SelectList = Nothing
sxGenderList = GetGenderList(MyPersonal.Gender)
ViewData.Add("Gender", sxGenderList)
ViewData.Add("FoundErrorInfo", FoundErrorInfo)
Return PartialView(MyPersonal)
sxGenderList = Nothing
End Function
在我看来，html如下
<tr>
<td class="FormFieldLabel" style="width: 30%;">Gender</td>
<td class="FormFieldLabel" style="width: 70%;">
<%= Html.DropDownListFor(Function(Model) Model.Gender, New SelectList(ViewData("Gender").Items, "ItemValue", "ItemText", "ItemSelected"), New With {.style = "font-family: Tahoma; font-size: 14pt; color: #333333;"})%>
<%= Html.ValidationMessageFor(Function(Model) Model.Gender)%>
</td>
</tr>
当我尝试编辑/更新中的视图时，SelectList/DropDown 始终显示列表中的第一个选项项，无论选择了什么。
它让我困惑了两天，我看不出它哪里出错了！请有人看看我的代码，看看它往西走。
提前致谢。