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Using Visual Studio 2022 to develop an ASP.NET web site a master page, when a meta element is part of a master page, a trailing slash gets automatically added to the element by the time the page is served. For example, if this appears in the master page:
<meta name="viewport" content="width=device-width, initial-scale=1.0">
it will appear to the browser (sources view, not element view) as:
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
When the meta element is part of an ASPX page (whether based on that master page or not), the trailing slash is not automatically added to the element. For example, if this appears in the ASPX page:
<meta name="viewport" content="width=device-width, initial-scale=1.0">
it will appear the same, without any additional trailing slash in the browser (sources view):
<meta name="viewport" content="width=device-width, initial-scale=1.0">
So, if the element is in the master page without a trailing slash, the trailing slash gets added automatically to the element by the time the browser sees it. If the element is in an ASPX page without a trailing slash, no trailing slash is automatically added. This is reproducible using the local "view page in browser" in Visual Studio, using either Edge or Chrome browsers, all with the latest updates. Why does a trailing slash get automatically added to meta elements appearing in an ASP.NET master page, but not when the meta elements appear in an ASPX page? Is there some master page setting in Visual Studio 2022 that controls whether trailing slashes are added? If so, where would I find it?
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There is no setting controlling this that I'm aware of. It is most likely a result of how the data is being written out. Meta tags are self-closing and shouldn't need the />. If you put one in then the browser will ignore it. There are some issues if you're targeting HTML5 vs XHTML though as XHTML would require them to be closed but HTML5 does not, IIRC.
Thanks for your response. I am targeting HTML5, with a DOCTYPE of html. The meta element is just there in the master page, with no trailing slash at its close. I would expect it to just appear "as is" in the served page, but all the meta elements get the trailing slash added to them when they originate in the master page. If the elements originate in the ASPX page instead, they appear unchanged in the served page, with no trailing slash.
I realize that the trailing slash is optional in HTML5, and it wouldn't have been an issue. But if I run the page through the Nu HTML Checker at validator.w3.org, each of the meta elements that originated from the master page get the message "Info: Trailing slash on void elements has no effect and interacts badly with unquoted attribute values." even though there is no trailing slash in the master page. This is what led me to discover that there was a difference in how meta elements in master pages as opposed to meta elements in ASPX pages were served. While this isn't that big a deal technically, I have a client who wants all pages in all of their sites to validate cleanly (no errors, warnings, or info messages) in this validator.
One workaround would be to move all these common meta elements out of the master page and into the individual ASPX pages, but that sort of defeats one of the purposes of using a master page and violates the DRY principle.
So, I'd really like to find out exactly why this is happening, and how to resolve it in a way that won't mean repeating code or doing something that's less readable/maintainable.
Off the top of my head I don't know why it would do that in the master file. Ultimately it uses HtmlTextWriter to write elements and the meta tag is marked as nonclosing.
But a workaround would be to move your meta tags into a user control (ascx) and then use that in the master page. The meta tags are then generated properly,