自定义 HtmlHelper 扩展方法在视图中不可用？

我翻译了耶利米·克拉克的MVC 的复选框列表助手进入我的 VB.Net 项目，但是当我尝试使用我认为的方法时，出现错误

'CheckBoxList' is not a member of 'System.Web.Mvc.HtmlHelper(Of Attenda.Stargate.Web.UserRolesViewModel)'.

谁能告诉我哪里出了问题？

辅助模块：

Imports System.Runtime.CompilerServices

Public Module InputExtensions

  <Extension()> _
  Public Function CheckBoxList(ByVal htmlHelper As HtmlHelper, ByVal name As String, ByVal listInfo As List(Of ListItem)) As String
    Return htmlHelper.CheckBoxList(name, listInfo, DirectCast(Nothing, IDictionary(Of String, Object)))
  End Function

  <Extension()> _
  Public Function CheckBoxList(ByVal htmlHelper As HtmlHelper, ByVal name As String, ByVal listInfo As List(Of ListItem), ByVal htmlAttributes As Object) As String
    Return htmlHelper.CheckBoxList(name, listInfo, DirectCast(New RouteValueDictionary(htmlAttributes), IDictionary(Of String, Object)))
  End Function

  <Extension()> _
  Public Function CheckBoxList(ByVal htmlHelper As HtmlHelper, ByVal name As String, ByVal listInfo As List(Of ListItem), ByVal htmlAttributes As IDictionary(Of String, Object)) As String
    If String.IsNullOrEmpty(name) Then
      Throw New ArgumentException("The argument must have a value", "name")
    End If
    If listInfo Is Nothing Then
      Throw New ArgumentNullException("listInfo")
    End If
    If listInfo.Count < 1 Then
      Throw New ArgumentException("The list must contain at least one value", "listInfo")
    End If
    Dim sb As New StringBuilder()
    For Each info As ListItem In listInfo
      Dim builder As New TagBuilder("input")
      If info.Selected Then
        builder.MergeAttribute("checked", "checked")
      End If
      builder.MergeAttributes(Of String, Object)(htmlAttributes)
      builder.MergeAttribute("type", "checkbox")
      builder.MergeAttribute("value", info.Value)
      builder.MergeAttribute("name", name)
      builder.InnerHtml = info.Text
      sb.Append(builder.ToString(TagRenderMode.Normal))
      sb.Append("<br />")
    Next
    Return sb.ToString()
  End Function

End Module

查看来源：

<%@ Page Title="" Language="VB" MasterPageFile="~/Views/Shared/TwoColumn.Master" Inherits="System.Web.Mvc.ViewPage(Of Attenda.Stargate.Web.UserRolesViewModel)" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
  Edit User Roles
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
  <h2>Edit Roles for
    <%=Html.Encode(Model.User.UserName)%></h2>
    <div>
    <%=Html.CheckBoxList("Roles", Model.Roles)%>
    </div>
</asp:Content>
<asp:Content ID="Content3" ContentPlaceHolderID="cphLeftPanel" runat="server">
</asp:Content>

您需要将包含自定义帮助器类的命名空间导入到您的视图页面中。您可以在页面本身或所有页面的 web.config 文件中执行此操作。首先将代码放入命名空间中。

<%@ Import Namespace="MyProject.Extensions" %>

或（在 web.config 中）

<pages>
   ...
   <namespaces>
       ...
       <add namespace="MyProject.Extensions" />
   </namespaces>
</pages>