How can I use Html.TextAreaFor() methods in my custom HtmlHelper?

Question

I'm building an ASP.NET MVC 2 website and right now, I have ugly spaghetti code in my view which I would like to make into a custom HtmlHelper. The current code in the view is :

            <%switch (Model.fiFieldTypeID) %>
            <%
            {
                case 1: // Text area
                    Response.Write(Html.Encode(Html.TextAreaFor(model => model.fiStrValue)));
                    Response.Write(Html.Encode(Html.ValidationMessageFor(model => model.fiStrValue)));
                    break;
                case 2: // Text box
                    Response.Write( Html.Encode(Html.TextBoxFor(model => model.fiStrValue)));
                    Response.Write( Html.Encode(Html.ValidationMessageFor(model => model.fiStrValue)));
                    break;
etc....

I was trying to encapsulate this code into a neat little HtmlHelper. This is how I started:

public class FormHelpers
{
    public static MvcHtmlString GetStreamFieldEditor(this HtmlHelper html, FieldInstance field)
    {
        string output = "";
        switch (field.fiFieldTypeID)
        {
            case 1: // Text area
                output += html.TextAreaFor(field=> field.fiStrValue).ToString();
etc....

I know my lamda is wrong... but my bigger concern is that TextAreaFor is not available as a method. However, plain old TextArea is available. I don't want to use TextArea because I need to preserve my model binding. How can I use TextAreaFor, TextBoxFor, etc, in my custom html helper?

Answer 1

Add using System.Web.Mvc.Html.
EDIT: Make sure you're referencing System.Web.Mvc.dll v2.0 or higher.

To fix the lambda, you need to manually generate an expression tree using System.Linq.Expressions.

Answer 2

How about this:

public static class FormHelpers
{
    public static MvcHtmlString GetStreamFieldEditor(
        this HtmlHelper<YourModelType> html)
    {
        var model = html.ViewData.Model;
        if (model.fiFieldTypeID == 1)
        {
            return html.TextAreaFor(x => x.fiStrValue);
        }
        return html.TextBoxFor(x => x.fiStrValue);
    }
}

And then:

<%: Html.GetStreamFieldEditor() %>
<%: Html.ValidationMessageFor(x => x.fiStrValue) %>