Custom HTML Helpers in MVC5 with Model Lambda

Question

I am trying to create a custom HTML helper that will result in an HTML editor appearing in an MVC app. I have been following the instructions at: http://dan.cx/2012/05/custom-strongly-typed-htmlhelpers-in-asp-net-mvc. I cannot get this to work and am completely stuck.

Here is the HtmlHelper that I have created.....

public static class HTMLEditor
{
    

    public static HtmlString RenderFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, int? width = 810, int? height = 200)
    {
        var name = html
                    .ViewContext
                    .ViewData
                    .TemplateInfo
                    .GetFullHtmlFieldName(ExpressionHelper.GetExpressionText(expression));
        var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);

        string myEditor = "<textarea id='" + name + "' ";
        myEditor += "class='textarea' placeholder='' style='width: " + width + "px !important; height: " + height + "px !important'></textarea>";
        myEditor += "<script>$('#" + name + "').wysihtml5({'html':true,'color': false,parser: function(html) {return html;}});";
        myEditor += "editor.on('load', function() {editor.focus();editor.composer.commands.exec('insertHTML', '" + metadata.Model + "');})";
        myEditor += "</script>";
        return new HtmlString(myEditor);
    }
}

Then, in my Razor view, I am attempting to use the helper like such...

@HTMLEditor.RenderFor(model => model.PageDetail.HTML)

However, everything compiles okay but when it comes time to render the view to the browser, I am receiving an error :

Compilation Error

Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS1501: No overload for method 'RenderFor' takes 1 arguments

I am not sure where the problem lies. I do see that the RenderFor method has two parameters, but I am unsure how to pass in a model instance value and have that value retained in the model instance after postback as well.

Any help here would be greatly appreciated.

Thanks Matt

As a side note, you can just use string name = ExpressionHelper.GetExpressionText(expression); and you should consider using TagBuilder to generate your html. — user3559349
– user3559349, Commented Oct 31, 2014 at 0:09

Ant · Accepted Answer · 2014-10-30 18:38:53Z

8

It looks to me like you're calling .RenderFor on the wrong object.

Your RenderFor method is an extension method of HtmlHelper. Therefore you should be calling @Html.RenderFor(model => ...) from the view.

answered Oct 30, 2014 at 18:38

Ant

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2 Comments

Solo812 Over a year ago

This worked! Thanks a lot Anthony. This is my first time attempting to use custom HTML helpers like this...

Ant Over a year ago

No problem :-) you were close!

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