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I have some questions about html helpers in ASP.NET MVC Framework. So...

  1. Can I override a inbuilt helper like @Html.HiddenFor?
  2. Should I override, or create a CustomHiddenFor one?

  3. While creating a Custom one, how can I change the value from ModelMetaData and then call the inbuilt helper? Eg:

    public static MvcHtmlString HiddenSecuredFor<TModel, TProperty>
    (this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes,bool secured)
{
    ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
    var name = ExpressionHelper.GetExpressionText(expression);
    if (!secured)
    {
        return htmlHelper.HiddenFor(expression,htmlAttributes);
    }

        // Here I want to change the value 
        // from the TModel lets say the property is x => x.Name
        // And I want to make the Name = "Mr. " + Name

    // Call the inbuild helper with the expression value changes.
    return htmlHelper.HiddenFor(expression, htmlAttributes);
}
Cristian E.
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1 Answers1

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  1. Yes - How can I override the @Html.LabelFor template?
  2. It depends - If you are adding functionality you always need and you want other developers to use without having to know about it, overriding is a good option. Otherwise, creating a custom one that calls the original is a good approach.
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severin
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  • Thank you for your answer and for the link. But what about the 3. ? – Cristian E. Mar 04 '14 at 09:26
  • I'm not sure if I understand exactly what you mean, but the metadata ultimately translates into htmlAttributes, so if you wish to add your own you can pass them on as htmlAttributes. Example: http://pastebin.com/BbzPSkhN – severin Mar 04 '14 at 09:43
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    `htmlAttributes` is simple to override but, how to change the actual value from the `expression`. When writing `@Html.HiddenFor(x => x.Name)`, we have 1. The expression tree which holds the property info(name,type etc). 2. The `@model MyNiceViewModel` which has the value of `x => x.Name`. How to change that value? – Cristian E. Mar 04 '14 at 09:48
  • I'm not sure if you can do that. My only suggestion would be to build the entire result yourself, like the initial example. – severin Mar 04 '14 at 09:55
  • Thank you for your suggestion. I'll do some experiments. If a better solution wouldn't appear from the community(including from you :)), I'll mark yours as an answer. – Cristian E. Mar 04 '14 at 10:01