Check RenderSectionAsync in _Layout is empty or not (ASP.NET Core MVC)

Question

This is my _Layout.cshtml:

@await RenderSectionAsync("SpecialHeader", required: false)

Some views have this and some don't:

@section SpecialHeader
{
    // something
}

So far so good.

Now how can I check whether RenderSectionAsync (in _Layout.cshtml) is null (empty) or not?

I want something like this:

if (RenderSectionAsync == null)   // this is in my mind
{
    // Public Header
}
else
{
    @await RenderSectionAsync("SpecialHeader", required: false)
}

Answer 1

You can use RazorPage.IsSectionDefined(string) method to check if the specified section is defined in the content page.

In the _Layout.cshtml page, add the following code:

@if (IsSectionDefined("SpecialFooter"))
{
    @await RenderSectionAsync("SpecialFooter", required: false)
}
else{
    <div>Default Content</div>
    @* IgnoreSection("SpecialFooter"); *@
}

Then in the content page:

Index page: define the section.

@section SpecialFooter {
    <div>custom footer</div>
}

Privacy page: without define the section.

The result as below:

Index page:

Privacy page: