Asp.net mvc 如何从扩展方法访问ValidationMessageFor

我怎样才能访问html扩展…比如LabelFor、EditorFor、ValidationMessageFor

我正在写我自己的扩展名

Imports System
Imports System.Web.Mvc
Imports System.Web.Mvc.Html
Imports System.Web
Imports System.Text

Public Module HtmlExtensions
    <System.Runtime.CompilerServices.Extension()> _
    Public Function Asistente(Of TModel As Class)(ByVal helper As HtmlHelper, model As TModel) As MvcHtmlString
        helper.ValidationMessage("Home") 'It works fine
        helper.ValidationMessagefor()    'It show the next message 'ValidationMessagefor' is not a member of 'System.Web.Mvc.HtmlHelper     
    End Function

...

实际上，这是因为我想生成一个这样的mvchtml字符串

<div class="editor-label">
    @Html.LabelFor(Function(model) model.Numero)
</div>
<div class="editor-field">
    @Html.EditorFor(Function(model) model.Numero)
    **@Html.ValidationMessageFor(Function(model) model.Numero)**
</div>

提前考虑

ValidationMessageFor方法需要一个泛型类型的html帮助程序。因此，您的方法可能如下所示：

Public Shared Function Asistente(Of TModel, TProperty)(helper As HtmlHelper(Of TModel), expression As Expression(Of Func(Of TModel, TProperty))) As HtmlString
    Return helper.ValidationMessageFor(expression)
End Function

Public Shared Function Test(Of T As User)(helper As HtmlHelper(Of T), model As T) As HtmlString
    Return helper.ValidationMessageFor(Function(f) f.Name)
End Function

这将允许您对任何型号使用该扩展，并且您的呼叫不会改变。不过我不完全确定你在问什么

**@Html.Asistente(Function(model) model.Numero)**

请注意，vb是使用c到vb转换器生成的，但它看起来是正确的

如果你想使用你发布的第一个示例，那么你必须这样写：

Public Shared Function Asistente(Of TModel, TProperty)(helper As HtmlHelper(Of TModel), expression As Expression(Of Func(Of TModel, TProperty))) As HtmlString
    Return helper.ValidationMessageFor(expression)
End Function

Public Shared Function Test(Of T As User)(helper As HtmlHelper(Of T), model As T) As HtmlString
    Return helper.ValidationMessageFor(Function(f) f.Name)
End Function

但是，这是一个特定的用例，因为如果不将模型类型强制为特定类型，则不会显示lambda表达式属性，因此也不会编译