How can you define sections with default content in MVC 6?

Question

I am currently trying to migrate an ASP.net MVC 5 project to MVC 6.

How would I migrate the following code:

public static class SectionExtensions
{
    public static HelperResult RenderSection(this WebPageBase webPage, [RazorSection] string name, Func<dynamic, HelperResult> defaultContents)
    {
        return webPage.IsSectionDefined(name) ? webPage.RenderSection(name) : defaultContents(null);
    }
}

[RazorSection] is part of the JetBrains.Annotations assembly.

Answer 1

Instead of WebPageBase I used RazorPage in Microsoft.AspNet.Mvc.Razor

namespace Stackoverflow
{
    public static class SectionExtensions
    {
        public static IHtmlContent RenderSection(this RazorPage page, [RazorSection] string name, Func<dynamic, IHtmlContent> defaultContents)
        {
            return page.IsSectionDefined(name) ? page.RenderSection(name) : defaultContents(null);
        }
    }
}

Then reference the class in the razor page @using static Stackoverflow.SessionExtensions, and call it like so:

@this.RenderSection("extra", @<span>This is the default!</span>))

An alternative way would be to just do this in the view (I prefer this way, seems a lot simpler):

@if (IsSectionDefined("extra"))
{
    @RenderSection("extra", required: false)
}
else
{
    <span>This is the default!</span>
}

I hope this helps.

Update 1 (from comments)

by referencing the namespace

@using Stackoverflow

you don't have to include the static keyword, but when calling it, you will have to reference the actual class in the namespace and also pass 'this' into the function.

@SectionExtensions.RenderSection(this, "extra", @<span>This is the default!</span>)

Update 2

There is a bug in razor that does not allow you to call template delegates Func <dynamic, object> e = @<span>@item</span>; within a section. Please see https://github.com/aspnet/Razor/issues/672

A current workaround:

public static class SectionExtensions
{
    public static IHtmlContent RenderSection(this RazorPage page, [RazorSection] string name, IHtmlContent defaultContents)
    {
        return page.IsSectionDefined(name) ? page.RenderSection(name) : defaultContents;
    }
}

and then the razor page:

section test {
    @this.RenderSection("extra", new HtmlString("<span>this is the default!</span>")); 
}