You can give your users the ability to store any data they want, including stuff they make up at run time, by using an ExpandoObject. In fact, when you don't know what your data is until run time (and you can live without IntelliSense), an ExpandoObject is your best solution.
The reality is that you will need to have, at least, two different configurations: one for production and one for development. Here's how to automate those conversions.
If you move beyond the basics of working with Razor Pages, there are at least two things you should know to support creating Pages that do more than one thing and integrate with existing code.
If you're moving your application's client-side code to Blazor, then you'll want Blazor to manage navigating between pages, too.
There are lots of ways to handle databases in a containerized environment like Docker. Here's how to create SQL Server in a container, how to load it with the data you want and how to integrate that container into whatever project needs it. Be warned: Some PowerShell is used.
Here's how to run a "real-world" application (consisting of an MVC application and a Web Service) in a networked set of Docker containers. And it's just a couple of mouse clicks in Visual Studio to implement it.
If you want to handle the most common pattern in ASP.NET Controllers (displaying a page and then accepting data entered into it), you can do it with Razor Pages. You'll just need less code than if you used a Controller, a View and a model object.
As fond as he is of using Controllers and Views, Peter isn't sure that Razor Pages aren't a better model for Web development. But the first step, adding Razor Pages to your project, isn't as easy as it should be. And, after that, you'll want to integrate them with your existing MVC application.
In ASP.NET Core, your web.config file with its <appsettings> section is gone. The replacement is a more extensive and configurable system that you can leverage to simplify configuring your objects.
ASP.NET Core's support for sharing objects defined at startup is great ... but what if you need to set options on those objects? Here's a case study that starts off great and then descends into over-engineered madness (but only if you want to go that far).
If you want to treat your database design as an "implementation detail" that just falls out of getting your object model right, then Entity Framework gives you four choices. Picking the right one, however, may mean creating your own.
Here's everything you need to write code for the Session object in ASP.NET Core -- including why you can't expect to migrate your existing ASP.NET MVC application to ASP.NET MVC Core (though Peter has some suggestions on easing that pain).
If you know how to create an ASP.NET MVC View, you know a great deal about how to create pages in Blazor. But, by packaging up pages as Blazor Components, you can use (and re-use) those pages more like objects.
Central to ASP.NET Core is the collection of objects that give you access to ASP.NET Core functionality. Here's how to access it, how to add to it and an example of how to use this technology with the "difficult" cases.
If you're a programmer then you know that you frequently get things wrong. Sometimes you find those bugs before your application gets to production ... and sometimes you don't. Bad news: Nothing is going to help and it's not going to get any better.