Use List<T> instead of ICollection in BehaviorDataObject

[halgab]

Finish work started in #8673
Related: #8140

Now that DropSourceBehavior is passed a List<IComponent> in its constructor, we can update BehaviorDataObject to do the same instead of using ICollection

Proposed changes

• Refactor BehaviorDataObject.DragComponents to be a List<IComponent> and update code accordingly
• Another small BehaviorDataObject refacto while we're touching this code, but in a separate commit

Microsoft Reviewers: Open in CodeFlow

[elachlan]

dragComps can now be IComponent[]

[halgab]

It doesn't look that simple... OleDragDropHandler.GetDraggingObjects return an object[]. I think it can be refactored to return an IComponent[], but that's more involved. I'm not sure I should add it to this PR

[halgab]

Looking at it again, it might be possible, but I'm not comfortable with making such a change. That would lead to assumptions that I'm not sure would hold all the time.

[elachlan]

Yeah, it depends if the team ever decided to implement another Component interface.

[elachlan]

As apart of this change maybe refactor this?

winforms/src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/TableLayoutPanelDesigner.cs

Lines 967 to 977 in cc1a968

	private Control ExtractControlFromDragEvent(DragEventArgs de)
	{
	DropSourceBehavior.BehaviorDataObject data = de.Data as DropSourceBehavior.BehaviorDataObject;
	if (data is not null)
	{
	dragComps = new ArrayList(data.DragComponents);
	return dragComps[0] as Control;
	}
	return null;
	}

Something like:

private Control ExtractControlFromDragEvent(DragEventArgs de) =>
    (de.Data as DropSourceBehavior.BehaviorDataObject)?.DragComponents.FirstOrDefault() as Control;

[halgab]

As apart of this change maybe refactor this?

winforms/src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/TableLayoutPanelDesigner.cs

Lines 967 to 977 in cc1a968

	private Control ExtractControlFromDragEvent(DragEventArgs de)
	{
	DropSourceBehavior.BehaviorDataObject data = de.Data as DropSourceBehavior.BehaviorDataObject;
	if (data is not null)
	{
	dragComps = new ArrayList(data.DragComponents);
	return dragComps[0] as Control;
	}
	return null;
	}

Something like:

private Control ExtractControlFromDragEvent(DragEventArgs de) =>
    (de.Data as DropSourceBehavior.BehaviorDataObject)?.DragComponents.FirstOrDefault() as Control;

Nice catch, I hadn't noticed this one. dragComps is a field though, so we have to keep it around. We could definitely change it to be a List<IComponent> after DragComponents itself becomes generic. As it's a change to a field in another type, perhaps is it more suited to a follow-up PR?

[elachlan]

I agree, follow up PR to make this change quicker to review.

[JeremyKuhne]

Thanks!

[halgab]

I agree, follow up PR to make this change quicker to review.

#10287