Last week I run intro an annoying little problem with the ASP.Net MVC 5 template. I created a new MVC web application for .Net 4.8 and after updating the packages it looked like this:
The most visible error of the design is the missing navigation bar, but there are additional problems that will pop up if you continue to build your application. It took me a while to figure out what the source of this problem is. As it turns out, the Visual Studio template still uses Bootstrap 3 and a package update in NuGet installs version 4. Bootstrap 4 was a major rewrite and navbar was one of parts that had breaking changes.
The quick fix
We can fix this problem by installing version 3.4.1 of the Bootstrap NuGet package:
If we now run the application, the navbar is back and everything works as expected:
Downgrading to Bootstrap 3 is a fast solution for demo applications. Be aware that Bootstrap 3 is no longer supported.
The better and durable fix
If you build an application for production, downgrading to an unsupported version is a bad idea. Instead, upgrade the template to Bootstrap 4 or Bootstrap 5. That takes more time, but if you do that right after Create a new project you only need to update a few pages.
This happened to me with Bootstrap 5. It work fine for a couple of weeks. Then “broke”. I have no idea what changed?