在另一个HTML Helper方法中将HTML Helper方法作为参数传递

Question

I have a Html Helper method that checks if a Section is defined and if not it should write out a partial file.

For this method I can pass a long string (the partial is rather big) or maybe I could pass the actual method @Html.RenderPartial(..) which would be much more efficient in my opinion (or is it negligible?).

Although I dont know how I could pass the @Html.RenderPartial(..) method as a parameter in the following function? Should I create a delegate?

    public static HelperResult RenderSectionEx(this WebPageBase webPage, 
                                                string name, ??? defaultContents)
    {
        if (webPage.IsSectionDefined(name))
            return webPage.RenderSection(name);
        else return defaultContents(null);
    }

Usage:

@this.RenderSectionEx("MetaTags", Html.Partial("~/Views/Shared/Partials/MetaTags.cshtml"))

What would be nice is to have the ability to pass both strings or a function in this method so I could pass small strings, for eg;

@this.RenderSectionEx("Title", @<h1>blah</h1>)

@this.RenderSectionEx("MetaTags", Html.Partial("~/Views/Shared/Partials/MetaTags.cshtml"))

Answer 1

Not sure if this will work (don't have a place to test at the moment) but you could create a delegate which would mean the partial is not called unless absolutely necessary:

public static IHtmlString RenderSectionEx(this WebPageBase webPage, 
                                          string name, 
                                          Func<IHtmlString> defaultContentMethod)
{
    if (webPage.IsSectionDefined(name))
        return webPage.RenderSection(name);

    return defaultContentMethod();
}

Then call it in your views like this:

@RenderSectionEx("blah", () => Html.Partial("~/Views/Shared/Partials/MetaTags.cshtml"))

And overload it for string instead of delegate:

public static IHtmlString RenderSectionEx(this WebPageBase webPage, 
                                          string name, 
                                          string defaultContent)
{
    if (webPage.IsSectionDefined(name))
        return webPage.RenderSection(name);

    return defaultContent;
}