MVC3 VB Razor无法识别转换后的C＃HTML扩展方法代码

Question

我一直在查看Google搜索结果，了解实现某种RadioButton列表（VB，MVC3，Razor）的方法。不幸的是，我发现的大多数结果都是在C＃中;这是我能找到的最有用的参考： Jon Lanceley's MVC3 RadioButton Helper （C＃，顺便说一句），所以我需要将代码翻译成VB（谢谢， developerFusion ！）。

我认为它会相当直接，但我发现编译器不会将该函数识别为模块命名空间的一部分;随之而来的是一些解决问题的尝试，但都失败了。

这是我的代码（您可以看到我通过评论尝试过的所有尝试，如果Andrew.San，则使用Ctrl + F签名）：

助手：

Imports System.Collections.Generic
Imports System.Linq
Imports System.Web
Imports System.Web.Mvc
Imports System.Web.Mvc.Html
Imports System.Linq.Expressions
Imports System.Runtime.CompilerServices
Imports System.Text

Namespace RadioButtonListForHelperTest
    Public Module HtmlExtensions

        Sub New()

        End Sub

        <Extension()> _
        Public Function RadioButtonForSelectList(Of TModel, TProperty)( _
                                                                          htmlHelper As HtmlHelper(Of TModel), _
                                                                          expression As Expression(Of Func(Of TModel, TProperty)), _
                                                                          listOfValues As IEnumerable(Of SelectListItem)) As MvcHtmlString
            Dim metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData)
            Dim stringBuilder = New StringBuilder()

            If listOfValues IsNot Nothing Then
                ' Create a radio button for each item in the list 
                For Each item As SelectListItem In listOfValues
                    ' Generate an id to be given to the radio button field 
                    Dim id = String.Format("{0}_{1}", metaData.PropertyName, item.Value)

                    ' Create and populate a radio button using the existing html helpers 
                    Dim label = htmlHelper.Label(id, HttpUtility.HtmlEncode(item.Text))
                    Dim radio = htmlHelper.RadioButtonFor(expression, item.Value, New With { _
                     Key .id = id _
                    }).ToHtmlString()

                    ' Create the html string that will be returned to the client 
                    ' e.g. <input data-val="true" data-val-required="You must select an option" id="TestRadio_1" name="TestRadio" type="radio" value="1" /><label for="TestRadio_1">Line1</label> 
                    stringBuilder.AppendFormat("<div class=&quot;RadioButton&quot;>{0}{1}</div>", radio, label)
                Next
            End If

            Return MvcHtmlString.Create(stringBuilder.ToString())
        End Function
    End Module
End Namespace

型号：

Imports System.Collections.Generic
Imports System.Linq
Imports System.Web
Imports System.ComponentModel.DataAnnotations
Imports System.Web.Mvc

Namespace RadioButtonListForHelperTest.Models
    Public Class TestModel
        Public Property TestRadioList() As IEnumerable(Of SelectListItem)
            Get
                Return m_TestRadioList
            End Get
            Set(value As IEnumerable(Of SelectListItem))
                m_TestRadioList = value
            End Set
        End Property
        Private m_TestRadioList As IEnumerable(Of SelectListItem)
        Public Property TestRadioList2() As IEnumerable(Of SelectListItem)
            Get
                Return m_TestRadioList2
            End Get
            Set(value As IEnumerable(Of SelectListItem))
                m_TestRadioList2 = value
            End Set
        End Property
        Private m_TestRadioList2 As IEnumerable(Of SelectListItem)

        <Display( _
            Name:="Test Radio 1", _
            Description:="This is the first list.", _
            Prompt:="Some prompt message.", _
            Order:=2)> _
        <Required(ErrorMessage:="You must select an option for TestRadio")> _
        Public Property TestRadio() As String
            Get
                Return m_TestRadio
            End Get
            Set(value As String)
                m_TestRadio = value
            End Set
        End Property
        Private m_TestRadio As String

        <Display( _
            Name:="Test Radio 2", _
            Description:="This is the second list.", _
            Prompt:="Some prompt message.", _
            Order:=1)> _
        <Required(ErrorMessage:="You must select an option for TestRadio2")> _
        Public Property TestRadio2() As String
            Get
                Return m_TestRadio2
            End Get
            Set(value As String)
                m_TestRadio2 = value
            End Set
        End Property
        Private m_TestRadio2 As String

        ' I tried it out, just in case 
        ' (see Index; @Html.RadioButtonForSelectList).
        ' It didn't help, really.
        ' - Andrew.San
        Public Function RadioButtonForSelectList(Of TModel, TProperty)( _
                                                                          htmlHelper As HtmlHelper(Of TModel), _
                                                                          expression As Expressions.Expression(Of Func(Of TModel, TProperty)), _
                                                                          listOfValues As IEnumerable(Of SelectListItem)) As MvcHtmlString
            Return RadioButtonListForHelperTest.RadioButtonForSelectList(htmlHelper, expression, listOfValues)
        End Function
    End Class

    Public Class aTest
        Public Property ID() As Integer
            Get
                Return m_ID
            End Get
            Set(value As Integer)
                m_ID = value
            End Set
        End Property
        Private m_ID As Integer
        Public Property Name() As String
            Get
                Return m_Name
            End Get
            Set(value As String)
                m_Name = value
            End Set
        End Property
        Private m_Name As String
    End Class
End Namespace

控制器：

Imports System.Collections.Generic
Imports System.Linq
Imports System.Web
Imports System.Web.Mvc
Imports RadioButtonListForHelperTest.RadioButtonListForHelperTest.Models

Namespace Controllers
    Public Class TestController
        Inherits System.Web.Mvc.Controller

        '
        ' GET: /Test

        Function Index() As ActionResult
            Dim list As New List(Of aTest)()
            list.Add(New aTest() With { _
             .ID = 1, _
             .Name = "Line1" _
            })
            list.Add(New aTest() With { _
             .ID = 2, _
             .Name = "Line2" _
            })
            list.Add(New aTest() With { _
             .ID = 3, _
             .Name = "Line3" _
            })
            Dim sl As New SelectList(list, "ID", "Name")

            Dim list2 As New List(Of aTest)()
            list2.Add(New aTest() With { _
             .ID = 1, _
             .Name = "test1" _
            })
            list2.Add(New aTest() With { _
             .ID = 2, _
             .Name = "test2" _
            })
            Dim sl2 As New SelectList(list2, "ID", "Name")

            Dim model = New TestModel()
            model.TestRadioList = sl
            model.TestRadioList2 = sl2

            model.TestRadio = "2"
            ' Set a default value for the first radio button helper
            Return View(model)
        End Function

        '
        ' POST: /Test

        <HttpPost()> _
        Public Function Index(model As TestModel, returnUrl As String) As ActionResult
            If ModelState.IsValid Then
                ModelState.AddModelError("", "Always force an error to be raised so we can test the postback sets the radio buttons to their last values.")
            End If

            ' If we got this far, something failed, redisplay form 
            Dim list As New List(Of aTest)()
            list.Add(New aTest() With { _
             .ID = 1, _
             .Name = "Line1" _
            })
            list.Add(New aTest() With { _
             .ID = 2, _
             .Name = "Line2" _
            })
            list.Add(New aTest() With { _
             .ID = 3, _
             .Name = "Line3" _
            })
            Dim sl As New SelectList(list, "ID", "Name")

            Dim list2 As New List(Of aTest)()
            list2.Add(New aTest() With { _
             .ID = 1, _
             .Name = "test1" _
            })
            list2.Add(New aTest() With { _
             .ID = 2, _
             .Name = "test2" _
            })
            Dim sl2 As New SelectList(list2, "ID", "Name")

            model.TestRadioList = sl
            model.TestRadioList2 = sl2

            Return View(model)
        End Function

    End Class
End Namespace

查看：

@Imports RadioButtonListForHelperTest <!-- Andrew.San - Looked up Google on how to import a namespace in VB -->
@ModelType RadioButtonListForHelperTest.RadioButtonListForHelperTest.Models.TestModel

@Code
    Dim obj1 As System.Web.Mvc.HtmlHelper(Of RadioButtonListForHelperTest.RadioButtonListForHelperTest.Models.TestModel)
    Dim obj2 As System.Web.Mvc.HtmlHelper(Of RadioButtonListForHelperTest.RadioButtonListForHelperTest.Models.TestModel)
    ViewData("Title") = "Index"
End Code

<h2>Index</h2>

<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

@Using Html.BeginForm()
    @Html.ValidationSummary(True)
    @<fieldset>
        <legend>TestModel</legend>

        <div class="editor-label">
            @Html.LabelFor(Function(model) model.TestRadio)
        </div>
        <div class="editor-field">
            @Html.RadioButtonForSelectList(Function(model) model.TestRadio, Model.TestRadioList)
            <!-- Andrew.San
                Apparently, the method isn't a member of 
                System.Web.Mvc.HtmlHelper(Of RadioButtonListForHelperTest.RadioButtonListForHelperTest.Models.TestModel),
                which is odd; I don't see the need for a Model to have this method. 
            -->

            @RadioButtonListForHelperTest.RadioButtonListForHelperTest.RadioButtonForSelectList(obj1, Function(model) model.TestRadio, Model.TestRadioList)
            <!-- Andrew.San
                The compiler needs me to send an htmlHelper argument to the 
                HtmlExtension RadioButtonForSelectList method, 
                which Jon Lanceley didn't need to do.

                @Html.RadioButtonForSelectList(m => m.TestRadio, Model.TestRadioList)
            -->

            @Html.ValidationMessageFor(Function(model) model.TestRadio)
        </div>

        <div class="editor-label">
            @Html.LabelFor(Function(model) model.TestRadio2)
        </div>
        <div class="editor-field">
            <!-- Andrew.San
                As per the first radio button list. 
            -->
            @Html.RadioButtonForSelectList(Function(model) model.TestRadio2, Model.TestRadioList2)
            @RadioButtonListForHelperTest.RadioButtonListForHelperTest.RadioButtonForSelectList(obj2, Function(model) model.TestRadio2, Model.TestRadioList2)
            @Html.ValidationMessageFor(Function(model) model.TestRadio2)
        </div>

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

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

右。这就是我所拥有的一切。

Answer 1

问题是您的扩展方法位于RadioButtonListForHelperTest命名空间中，但在您的视图中，您尝试访问它时会查看System.Web.Mvc.Html命名空间。 @Html位于System.Web.Mvc。

要在同一名称空间中访问您的扩展方法，您需要执行以下操作。

将当前名称空间更改为System.Web.Mvc.Html。然后创建一个名为任意名称的静态类MyExtensions，然后在此类中包含扩展方法。它必须是静态的。