Generic used in conjunction with Sort(Comparison)

Question

Im wondering if its possible to reuse my overload of the Sort(Comparison) method to sort both labels and textboxes by tabIndex. Ive already tried and i couldnt get it to work. Any help would be appreciated.

foreach(Control control in gbUserInputs.Controls)
        {
            if (control is Label)
            {
                inputLabels.Add((Label)control);
            }

            if (control is TextBox)
            {
                inputTxtboxes.Add((TextBox)control);
            }
        }

Sort method call(this doesnt work).

inputLabels.Sort(sortMyInputs<Label>);

Overload of sort method.

private static int sortMyInputs<T>(T entry1, T entry2)
    {
        return entry1.TabIndex.CompareTo(entry2.TabIndex);
    }

Answer 1

You shouldn't be making a generic method:

private static int CompareLabels(Label entry1, Label entry2)
{
    return entry1.TabIndex.CompareTo(entry2.TabIndex);
}

The point of a generic delegate is to allow it to hold methods of different concrete types; not to allow it to hold methods that are themselves generic.

If you want to reuse your method, you can modify it to take Control (which both TextBox and Label inherit); you would still be able to pass it to List<Label>.Sort because of delegate covariance.

---

If you're using .Net < 4, which doesn't have delegate covariance, you can do it your way by adding a constraint to the method so that it knows what T can be:

private static int CompareLabels<T>(T entry1, T entry2) where T : Control
{
    return entry1.TabIndex.CompareTo(entry2.TabIndex);
}

---

You can also simply replace all of your code with one line of LINQ:

inputLabels = gbUserInputs.Controls.OfType<Label>()
                                   .OrderBy(c => c.TabIndex)
                                   .ToList();