Custom htmlhelper with validation support

Question

I create my own HtmlHelper to enable AutoFill in the selection list .

This works fine, except that I need to support DataAnnotations in my ViewModel.

Here is my current (working) HtmlHelper (sans validation)

    <Extension()>
    Public Function AutoCompleteDropDownList(ByVal helper As HtmlHelper, name As String, autoCompleteSelectListItem As List(Of AutoCompleteSelectListItem), htmlAttributes As Object) As MvcHtmlString
        Dim selectBuilder As New TagBuilder("select")
        selectBuilder.MergeAttribute("name", name)
        selectBuilder.MergeAttributes(New RouteValueDictionary(htmlAttributes))
        selectBuilder.MergeAttribute("autocorrect", "off")
        selectBuilder.MergeAttribute("autocomplete", "off")

        Dim selectListBuilder As New TagBuilder("option")
        selectListBuilder.MergeAttribute("value", "")
        selectListBuilder.MergeAttribute("selected", "selected")

        Dim innerHtmlBuilder As New StringBuilder
        innerHtmlBuilder.Append(selectListBuilder.ToString(TagRenderMode.Normal))


        For Each item In autoCompleteSelectListItem
            selectListBuilder = New TagBuilder("option")
            selectListBuilder.MergeAttribute("value", item.Value)
            selectListBuilder.MergeAttribute("data-alternative-spellings", item.AlternativeSpellings)
            selectListBuilder.MergeAttribute("data-relevancy-booster", item.RelevancyBooster)
            selectListBuilder.InnerHtml = item.Label
            innerHtmlBuilder.Append(selectListBuilder.ToString(TagRenderMode.Normal))
        Next

        selectBuilder.InnerHtml = innerHtmlBuilder.ToString()

        Return MvcHtmlString.Create(selectBuilder.ToString(TagRenderMode.Normal))
    End Function

How can I rewrite this to support validation? Sort ofAutoCompleteDropDownListFor()

PS: the C # solution is quite acceptable, the project I'm working on is in VB, but I am not against the translation.

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PS: I am browsing the source code of http://aspnet.codeplex.com and I cannot find the link toDropDownListFor

Answer 1

, DropDownListFor mvc3-rtm-sources.zip\mvc3-rtm-sources\mvc3\src\SystemWebMvc\Mvc\Html\SelectExtensions.cs. , HTML5 * . SelectInternal, htmlHelper.GetUnobtrusiveValidationAttributes.

<Extension()>
Public Function AutoCompleteDropDownList(ByVal helper As HtmlHelper, name As String, autoCompleteSelectListItem As List(Of AutoCompleteSelectListItem), htmlAttributes As Object) As MvcHtmlString
    Dim selectBuilder As New TagBuilder("select")
    selectBuilder.MergeAttribute("name", name)
    selectBuilder.MergeAttributes(New RouteValueDictionary(htmlAttributes))
    selectBuilder.MergeAttribute("autocorrect", "off")
    selectBuilder.MergeAttribute("autocomplete", "off")

    Dim selectListBuilder As New TagBuilder("option")
    selectListBuilder.MergeAttribute("value", "")
    selectListBuilder.MergeAttribute("selected", "selected")

    Dim innerHtmlBuilder As New StringBuilder
    innerHtmlBuilder.Append(selectListBuilder.ToString(TagRenderMode.Normal))


    For Each item In autoCompleteSelectListItem
        selectListBuilder = New TagBuilder("option")
        selectListBuilder.MergeAttribute("value", item.Value)
        selectListBuilder.MergeAttribute("data-alternative-spellings", item.AlternativeSpellings)
        selectListBuilder.MergeAttribute("data-relevancy-booster", item.RelevancyBooster)
        selectListBuilder.InnerHtml = item.Label
        innerHtmlBuilder.Append(selectListBuilder.ToString(TagRenderMode.Normal))
    Next

    selectBuilder.InnerHtml = innerHtmlBuilder.ToString()
    selectBuilder.MergeAttributes(helper.GetUnobtrusiveValidationAttributes(name))

    Return MvcHtmlString.Create(selectBuilder.ToString(TagRenderMode.Normal))
End Function

---

UPDATE:

, :

<Extension()>
Public Function AutoCompleteDropDownListFor(Of TModel, TProperty)(helper As HtmlHelper(Of TModel), expression As Expression(Of Func(Of TModel, TProperty)), autoCompleteSelectListItem As List(Of AutoCompleteSelectListItem), htmlAttributes As Object) As IHtmlString
    Dim name = ExpressionHelper.GetExpressionText(expression)
    Dim fullHtmlFieldName As String = helper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name)

    Dim selectBuilder = New TagBuilder("select")
    selectBuilder.MergeAttribute("name", fullHtmlFieldName)
    selectBuilder.MergeAttributes(New RouteValueDictionary(htmlAttributes))
    selectBuilder.MergeAttribute("autocorrect", "off")
    selectBuilder.MergeAttribute("autocomplete", "off")

    Dim selectListBuilder = New TagBuilder("option")
    selectListBuilder.MergeAttribute("value", "")
    selectListBuilder.MergeAttribute("selected", "selected")

    Dim innerHtmlBuilder = New StringBuilder()
    innerHtmlBuilder.Append(selectListBuilder.ToString(TagRenderMode.Normal))

    For Each item In autoCompleteSelectListItem
        selectListBuilder = New TagBuilder("option")
        selectListBuilder.MergeAttribute("value", item.Value)
        selectListBuilder.MergeAttribute("data-alternative-spellings", item.AlternativeSpellings)
        selectListBuilder.MergeAttribute("data-relevancy-booster", item.RelevancyBooster)
        selectListBuilder.InnerHtml = item.Label
        innerHtmlBuilder.Append(selectListBuilder.ToString(TagRenderMode.Normal))
    Next

    selectBuilder.InnerHtml = innerHtmlBuilder.ToString()
    selectBuilder.MergeAttributes(helper.GetUnobtrusiveValidationAttributes(name))

    Return MvcHtmlString.Create(selectBuilder.ToString(TagRenderMode.Normal))
End Function