Get input for unknown class fields during runtime

I've been learning C# the past couple of months and we've been tasked with a small project where there's this specific requirement:

We need to design the UI part of the project in such way, that we can figure out some random class fields and then get the input from a user to initialize those fields.

For example, in one run of the program we have this class A that has two integer fields. In the UI section, we need to figure out class A has two integers, then we need to receive 2 integers from the user and pass them back for initialization.

Another scenario:

We have class B that has a boolean and an Enum field, and we need to do the same.

I've been leaning towards using reflection to gather the data needed in runtime, but I'm having a lot of problem figuring out how to actually receive the required input from user. Another hurdle is that we were told that reflection isn't gonna help us and/or not required to fulfill this task.

I'm fairly inexperienced with the language so I assume there may be some other ways to implement this that I'm not aware of, but conceptually speaking - I really can't grasp how it is possible.

Here's some basic classes hierarchy to give a better example:

public abstract class Shape
{
    private Point location;
    private string color;
}

public abstract class NonCircular : Shape
{
    private int edgesNumber;
}

public class Circle : Shape
{
    private float radius;
    private float diameter;
}

public class Triangle : NonCircular
{
    public enum AngleType { Right, Acute, Obtuse }
    public enum EdgePropery { Equilateral, Isosceles, Scalene }
    private AngleType angleType;
    private EdgePropery edgePropery;
    private float angle1, angle2, angle3;
}

Going with this example - let's say that class 'Triangle' is being added to the solution later-on, after the project is done. We first construct the abstract class 'Shape' with some of the basic fields that are shared among everyone, and then according to the requirements, the UI needs to receive the fields:

angleType, edgePropery, and angles1-3

and pass back values to the logical part of the project in order to initialize them properly.