If you develop with #aspnetcore 2.0 or later and you are using TempData, you may run into a 400 error saying your request headers is too long. I've recently encountered this while writing a blog post, it happens when I try to preview the post.
Project source: https://github.com/FanrayMedia/Fanray
Blog post: https://www.fanray.com/post/2019/01/1...