Would like advice on how best to delegate tasks between the main form and its classes.

Question

I am trying to learn the proper way to program C# for Windows applications, and I have a question about the correct or best way to pass information between the main form and the classes that the form contains.

For example, let us say my form "Form1" contains a class "MyClass" that does most of the calculations, etc. The main form creates an instance of the MyClass class. Let us say, for example, that the user clicks a button on the form that then calls a function "MyFunction" contained in MyClass. The function MyFunction performs some tasks, and then based on the outcome of these tasks, then needs to update or change various controls located on the main form.

What is the best or proper way to do this? Should I send a reference to Form1 as an argument in the call to the MyClass function MyFunction, and then reference the Form1 controls from MyFunction directly? Or should I just set some public informational variables within MyFunction, then return from this function without doing anything to the Form1 controls, and then let the "on event" function in the main form which called MyFunction examine these public variables and then do the updates or changes to its controls?

I am wondering what is best from coding correctness, efficiency, and - very important also - understandability of the code to myself and future programmers.

Thanks for any advice!

Brandon Lewis · Answer

Your welcome :) Just remember that good design doesn't always mean taking the easiest route. You will be much better off in larger projects if you design well and keep things organized from early on

steve · Answer

Hi and thanks for the answer. Yes the way you describe is how I have started to do things with my first C# project. It has been extremely tempting to let my MyClass do the work on the main form directly. For example the user enters the name of an entity in a database and this name is passed to a function in MyClass that gets the entity and then produces an image to be displayed on the main form. The size of the image on the main form depends on which entity is retrieved from the database and I want to move other controls around based on this size. So it was tempting to manipulate the form controls directly from the function in MyClass rather than let the function in MyClass return and then call functions in the Form1 class to manipulate the Form1 controls. But I can see the point that it is far better from code organization (and for a more linear call stack) to do things as you describe. Thanks!

Brandon Lewis · Answer

You always want to make sure that you differentiate between the user interface and the assembly code. If you have some decision making to decide how to manipulate the interface with the form code itself thats fine. But if you can try to avoid sending form controls into classes if its not really necessary. Here is the break down of what I would do in your situation: User clicks the Calculate button. Two numbers are passed to MyClass.MyFunction as parameters MyFunction processes these numbers as necessary MyFunction returns the results of the calculation The Main Form is still waiting on a return results from MyFunction and receives it The Main Form updates its user interface appropriately displaying the result of the calculation If you understand how the call stack works it would make more sense. Example: Button_Click Eventhandler Method Button_Click Eventhandler Method calls MyClass.MyFunction MyClass.MyFunction does some calculations MyClass.MyFunction returns a result and its stack frame is removed from the calls stack Button_Click Eventhandler Method gets result from MyClass.MyFunction Button_Click Eventhandler Method updates user interface (or better calls another method to do it passing the new calculation as a parameter). Check out Functional Decomposition to get a better idea