ASP.Net MVC3 - Pass razor markup as a parameter

Question

I have a helper called EditableArea which provides a user with a runtime-editable div (via JS). EditableArea helper checks if an editable area (not

Answer 1

Just to expand on the accepted answer, as it took me quite a while to resolve a similar problem and this is the question which popped up. What I really need was a @helper, which would accept razor text, as the template should contain quite some code. I played around for a long while trying to use several versions of type @helper item(Func<object, HelperResult> input), which I found on the web, with no success. Therefore I went for an approach like:

namespace project.MvcHtmlHelpers
{
    public static class HelperExtensions
    {
        public static MvcHtmlString RazorToMvcString(this HtmlHelper htmlHelper, Func<object, HelperResult> template)
        {
            return MvcHtmlString.Create(template.Invoke(null).ToString());
        }
    }
}

and

@project.MvcHtmlHelpers    
@helper item(other input, MvcHtmlString content)
    {
        <div class="item">
            ...other stuff... 
            <div class="content">
                @content
            </div>
        </div>
    }

and use this via

@item(other input, @Html.RazorToMvcString(@<text>this is a test</text>))

Now I can use the helper template for both Razor input, but I can also drop in partial views, which is handy at some points. As I am no expert there might be better options, but it seems like a flexible approach to me.

Answer 2

Taking this further, it is possible to pass the markup directly to a helper, without an extension method.

@helper HelperWithChild(Func<object, HelperResult> renderChild)
{
    <div class="wrapper">
        @renderChild(this)
    </div>
}

@HelperWithChild(@<h1>Hello</h1>)

For multi-line markup <text> is required as well:

@HelperWithChild(@<text>
    @AnotherHelper()

    <h1>
        With more markup
    </h1>
</text>)

@helper AnotherHelper()
{
    <p>
        Another helper
    </p>
}

Though I'm not sure how this will play out with Model - my helpers only use their parameters.

Answer 3

Here's an example I use to render jQuery Template markup by passing in a template Id and razor-style syntax for the template itself:

public static MvcHtmlString jQueryTmpl(this HtmlHelper htmlHelper, 
    string templateId, Func<object, HelperResult> template) 
{
    return MvcHtmlString.Create("<script id=\"" + templateId + 
        "\" type=\"x-jquery-tmpl\">" + template.Invoke(null) + "</script>");
}

and this would be called with

@Html.jQueryTmpl("templateId", @<text>any type of valid razor syntax here</text>)

Basically just use Func<object, HelperResult> as your parameter and template.Invoke(null) (with arguments if necessary) to render it. Obviously you can skip the call to .Invoke() to avoid rendering the "default" markup.

Answer 4

In case you're wondering this is how to do it in asp.net core 3.1

@{
    void TemplateFunc(Func<object, IHtmlContent> template)
    {
        <div>@template(null)</div>
    }
}

Then in markup you can use it as

<div>
@{TemplateFunc(@<div>123</div>);}
</div>