Question

It is likely that I am going about this all wrong, but I have a user control called CategoryControl, there can be many like it, for that reason I decided that many of its functions would be better served as static methods. I wanted to know if there is a “better” way of accessing these methods then passing an instance all over the class. The methods are public static as they will be updated by other methods. The though of making extension methods comes to mind..?

public CategoryControl(UserCategory userCategory)
{
   InitializeComponent();

   PopulateControl(userCategory, this);
}

private static void PopulateControl(UserCategory userCategory, CategoryControl instance)
{

   SetCategoryTitle(userCategory, instance);

   SetPercentCorrect(userCategory, instance);

   SetQuestionsMissed(userCategory, instance);

   SetBackgroundBar(userCategory, instance);

   SetForegroundBar(userCategory, instance);

}

Updated::

The longer story is that I have a Panel on the screen, the panel contains relevant user categories. By relevant I mean that the user has the option of changing courses thus displaying a new set of categories. A user can also change the values of a category based on their interaction with the software. So…

A panel shows the categories of a course.

I maintain a list of the active Category Controls in the panel, and the main form tells the panel when to draw a new set of categories.

public void InitializeProgressPanel(UserCategories parentCategories)
{
   Contract.Requires(parentCategories != null, "parentCategories is null.");

   RemoveAllControlsFromList(_categoryControls);

   UserCategories sortedUserCategories = parentCategories.SortByWorst();

   int categoriesCount = parentCategories.Count();

   int spacer = (Height - (CategoryControl.Controls_Height * categoriesCount)) / categoriesCount+1;

   for (int i = 0; i < sortedUserCategories.Count; i++)
   {
      CategoryControl cc = new CategoryControl((UserCategory)sortedUserCategories[i]);

      cc.Left = 0;

      if (i == 0)
         cc.Top = spacer;
      else
         cc.Top = (Controls[i - 1].Bottom + spacer);

      Controls.Add(cc);
      _categoryControls.Add(cc);

      }
}

Answer 1

I would certainly not make extension methods if I had a class in hand that I could extend. Remember, the purpose of extension methods is to extend types that you cannot extend yourself.

The question at hand then is, should you say:

class C 
{
    public void Foo() { ... }
}

or

class C
{
    public static void Foo(C c) { ... }
}

I would ask some questions like:

• Is the class ever going to be subclassed? If so, should this be a virtual method?
• Is Foo the kind of thing that an instance does to itself, or the sort of thing that it has done to it? An animal eats on its own, but an animal is fed by someone else.

UPDATE:

Some more questions I’d ask myself:

• Are the properties and whatnot you are setting ever going to change? The less mutability you have in a class, the easier it is to test, the easier it is to reason about, and the fewer bugs you’ll have. If the properties and whatnot are never going to change then do not set them in any kind of method. Set them in the constructor and then never worry about them again; they’re correct.