Question

Ok, here’s what I’m trying to do… given this razor code

@using(Html.WriteLater())
{
    output line one
}
actual first line
@using(Html.WriteLater())
{
    output line two
}
actual second line

@HTML.WriteNow();

I want this output:

actual first line
actual second line
output line one
output line two

There are times when it is nice to logically group blocks of code together in the view, but the final output needs to be organized differently. I’ve tried ataching a different ViewContext in my helper logic but it doesn’t work:

public static WriteLaterContainer WriteLater( this HtmlHelper htmlHelper )
{
    ViewContext vc = new ViewContext();
    return new WriteLaterContainer( vc );
}

Answer 1

No idea why would you want to reinvent wheels instead of using standard approaches such as partials, sections, helpers, … but I guess you probably have some reasons. So not exactly the syntax you have shown but you could achieve similar results by using a conjunction of 2 helpers:

public static class HtmlExtensions
{
    private const string QueueKey = "_output_queue_";
    public static IHtmlString WriteLater(this HtmlHelper htmlHelper, Func<object, HelperResult> action)
    {
        var queue = htmlHelper.ViewContext.HttpContext.Items[QueueKey] as Queue<Func<object, HelperResult>>;
        if (queue == null)
        {
            queue = new Queue<Func<object, HelperResult>>();
            htmlHelper.ViewContext.HttpContext.Items[QueueKey] = queue;
        }
        queue.Enqueue(action);

        return MvcHtmlString.Empty;
    }

    public static IHtmlString WriteNow(this HtmlHelper htmlHelper)
    {
        var queue = htmlHelper.ViewContext.HttpContext.Items[QueueKey] as Queue<Func<object, HelperResult>>;
        if (queue == null)
        {
            return MvcHtmlString.Empty;
        }

        var writer = htmlHelper.ViewContext.Writer;
        foreach (var item in queue)
        {
            item(null).WriteTo(writer);
        }

        return MvcHtmlString.Empty;
    }
}

that could be used like this:

@Html.WriteLater(@<div>output line one</div>)
<div>actual first line</div>
@Html.WriteLater(@<div>output line two</div>)
<div>actual second line</div>
@Html.WriteNow()

and the output will be the expected one:

actual first line
actual second line
output line one
output line two