HtmlHelperExtensions are not visible in view mvc3 asp.net

Question

I've added a class for the HTML Custom Extensions:

using System;
using System.Linq.Expressions;
using System.Text;
using System.Web.Mvc;
using System.Web.Mvc.Html;

namespace App.MvcHtmlHelpers    
{
public static class HtmlHelperExtensions
{

    public static MvcHtmlString ComboBox(HtmlHelper html, string name, SelectList items, string selectedValue)
    {
        var sb = new StringBuilder();
        sb.Append(html.DropDownList(name + "_hidden", items, new { @style = "width: 200px;", @onchange = "$('input#" + name + "').val($(this).val());" }));
        sb.Append(html.TextBox(name, selectedValue, new { @style = "margin-left: -199px; width: 179px; height: 1.2em; border: 0;" }));
        return MvcHtmlString.Create(sb.ToString());
    }

    public static MvcHtmlString ComboBoxFor<TModel, TProperty>(HtmlHelper<TModel> html, Expression<Func<TModel, TProperty>> expression, SelectList items)
    {
        var me = (MemberExpression)expression.Body;
        var name = me.Member.Name;

        var sb = new StringBuilder();
        sb.Append(html.DropDownList(name + "_hidden", items, new { @style = "width: 200px;", @onchange = "$('input#" + name + "').val($(this).val());" }));
        sb.Append(html.TextBoxFor(expression, new { @style = "margin-left: -199px; width: 179px; height: 1.2em; border: 0;" }));
        return MvcHtmlString.Create(sb.ToString());
    }

I've also registered it in my site web config:

<namespaces>
<add namespace="System.Web.Helpers" /> 
<add namespace="System.Web.Mvc" />
<add namespace="System.Web.Mvc.Ajax" />        
<add namespace="System.Web.Mvc.Html" />
<add namespace="System.Web.Routing" />
<add namespace="System.Web.WebPages" />
<add namespace="App.MvcHtmlHelpers"/>
</namespaces>

In my view, I import the namespace:

<%@ Import Namespace="RSPWebApp.MvcHtmlHelpers" %>

But when I go to call it in the view, it doesn't recognize the custom extension. Can someone help me by telling me what I might have missed? Thanks so much in advance! <%:Html.ComboBoxFor(a => a.Street2, streetAddressListItems) %>

JofryHS · Accepted Answer · 2012-11-28 23:02:09Z

2

You might be missing this keyword:

public static MvcHtmlString ComboBox(this HtmlHelper html, string name, SelectList items, string selectedValue)

Also if check your Web.config in your Views directory for something similar to this:

<system.web.webPages.razor>
    <host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    <pages pageBaseType="System.Web.Mvc.WebViewPage">
      <namespaces>
        <add namespace="System.Web.Mvc" />
        <add namespace="System.Web.Mvc.Ajax" />
        <add namespace="System.Web.Mvc.Html" />
        <add namespace="System.Web.Routing" />
        <add namespace="RSPWebApp.MvcHtmlHelper" />
      </namespaces>
    </pages>
</system.web.webPages.razor>

It seems that instead of the project Web.config, you have to explicitly add the namespace to the Razor engine itself in the Views folder.

answered Nov 28, 2012 at 23:02

JofryHS

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2 Comments

MushinNoShin Over a year ago

I don't think we can tell if OP is using Razor views or not.

MVCKarl Over a year ago

@JofryHS, is correct, you are missing the "this" keyword and are putting the reference in the wrong Web.Config

MushinNoShin · Accepted Answer · 2012-11-28 22:57:21Z

You're missing the this keyword in your extension methods. Try this:

public static MvcHtmlString ComboBox(this HtmlHelper html, string name, SelectList items, string selectedValue)
    {
        var sb = new StringBuilder();
        sb.Append(html.DropDownList(name + "_hidden", items, new { @style = "width: 200px;", @onchange = "$('input#" + name + "').val($(this).val());" }));
        sb.Append(html.TextBox(name, selectedValue, new { @style = "margin-left: -199px; width: 179px; height: 1.2em; border: 0;" }));
        return MvcHtmlString.Create(sb.ToString());
    }

Also the Import Namespace you provided doesn't appear to be the same namespace as your extension methods. However adding them to the web.config should have you covered anyway.

silvenwolf · Accepted Answer · 2012-11-29 17:50:41Z

0

Thanks everyone for all your help. I was indeed missing the "this" keyword in my HTMLHelper class (it originally came up red in my resharper, so I shouldn't trust that all the time!)

And I added it to my web.config in the Views folder (although oddly it's grayed out) . To answer a previous comment I am actually using ASP.Net views as I'm new to MVC and didn't want to wrestle with Razor+MVC.

It works perfectly now, thank you!

answered Nov 29, 2012 at 17:50

silvenwolf

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