Update ObjectContainerHelper.GetCategoryOrder to use the TypeDescriptor to get attributes

[MarqueIV]

The existing code which simply called GetCustomAttributes doesn't take into consideration those attributes added via a TypeDescriptor. As such, you should use the TypeDescriptor.AddAttributes which gets both those defined on the class at compile time, plus those added at runtime.

Note: In a semi-related issue, here, the CategoryOrderAttribute needs to add the following override to work correctly.

public override object TypeId => CategoryValue;

I don't have the ability to create PRs or I'd submit this myself, but here's the needed function.

private int GetCategoryOrder(object categoryValue) {

  Debug.Assert(SelectedObject != null);

  if (categoryValue == null)
    return int.MaxValue;

  object selectedObject = SelectedObject;

  var orderAttribute = TypeDescriptor.GetAttributes(selectedObject)
      .OfType<CategoryOrderAttribute>()
      .FirstOrDefault(a => Equals(a.CategoryValue, categoryValue));

  return orderAttribute?.Order ?? int.MaxValue;
}

HTH!

Mark

[MarqueIV]

I figured out how to create a PR here, so I went ahead and created one. It's here... #1523

[XceedBoucherS]

Thank you.
This will be included in v3.9.