Question

I have several controls that all inherit from UserControl, and I have a MergeSort method that runs on UserControl types (to save me from writing out 6 different methods), but when I cast back to my custom controls after the sorting, it throws an error, what am I doing wrong? The mergesort method requires the Left property, which each custom control uses, so is there any other way I can do this?

MergeSort method looks like:

public UserControl[] MergeSort(UserControl[] array)

Cast looks like:

(CustomControl[])MergeSort(customControlArray);

Answer 1

I think you have to cast each of them manually:

CustomControl[] customControlArray;
...
UserControl[] sortedControls = MergeSort(customControlArray);
CustomControl[] sortedCustomControls = Array.ConvertAll<UserControl, CustomControl>(sortedControls, delegate(UserControl control)
{
    return (CustomControl)control;
});

If you have .NET 3.5+ at your disposal you can use much “cooler” syntax. 🙂

Edit: the cooler syntax is:

UserControl[] sortedControls = customControlArray.ToList().ConvertAll(c => (CustomControl)c).ToArray();

🙂