Choose a class based on the value in the combobox in C# 2019 - c#-4.0

Question

I have a MainForm window in my C# Window Application. In this form, I have a combo box with 3 values.
Values are Apple, Orange and Banana.
Also I have 3 other classes specifically for these combobox values. Suppose if the user choose Apple in the combobox,
then the class for Apple will be the working module. If the user chooses Banana in the combo, then the working module will be the Banana class.
For example, I run the app. MainForm is loaded. The user chooses Apple from the combobox. Then the class working with MainForm will be the Apple class. ie, In the MainForm, the object of the Apple will be created and access the methods of apple class. If the user chooses Banana, then there should be a way to chose the banana class as the working class with the Mainform. [ie, inside the mainform, the object of the Banana class is created and access the method of the banana
class].
In short, there are some methods in the Apple/Orange/Banana class. And I want to
update the value of these fruits to the labels in the MainForm. So, when I run
the application, the main form will be displayed and the user choose the Apple
value from the combo box. Then the current working module will be Apple class.
When the user click on a button in the Mainform, there is some calculation is going on in the Apple class and the value will be updated the label in the MainClass.[ie, value generated in the Apple class and displayed in the MainForm]
What would be the right way to do this. I am not getting an idea of it.

Answer 1

You could begin by defining a common interface/base class for the fruits. This would serve as the base for creating the collection to be bound to the ListBox. For example,
public interface IFruit
{
string FruitName { get; }
double GetPrice();
}
public class Apple : IFruit
{
public string FruitName => nameof(Apple);
public double GetPrice()
{
return 1.0;
}
}
public class Orange : IFruit
{
public string FruitName => nameof(Orange);
public double GetPrice()
{
return 2.0;
}
}
public class Banana : IFruit
{
public string FruitName => nameof(Banana);
public double GetPrice()
{
return 3.0;
}
}
Now, you could bind the Listbox by creating a List.
var fruitCollection = new List<IFruit>
{
new Apple(),
new Orange(),
new Banana(),
};
fruitListBox.DataSource = fruitCollection;
fruitListBox.DisplayMember = nameof(IFruit.FruitName);
Finally, when you need to execute a method on the selected Item, you could use
var price = (fruitListBox.SelectedItem as IFruit).GetPrice();