This is done is the alloy mvc templates. I would recommend that you take a look on how it is being done there.
The property is not on the layout view itself, but added on the start page. A edit hint connection is then added to make the property editable despite being in the layout view.
Thanks Per for pointing that out.
Is there any documentation on edit hint? I don't understand what it is and how it works.
In the SDK: Editing hints in MVC.
Can I have properties in the _Layout.cshtml file somehow?
The scenario I'm thinking of is to allow the editor to change the image file used as the logo for the site, a logo that resides within a layout file.
Since the layout is not part of a specific page, I'm not sure how I can bind properties to it?