Fix CollectionEditor Up/Down button enabled state for first/last items

[LeafShi1]

Fixes #14160

Root Cause

The UpdateEnabled() method in CollectionEditorCollectionForm only checked if the collection had more than one item (_listBox.Items.Count > 1) to enable the Up/Down buttons, but failed to verify the selected item's position in the list.

Proposed changes

• Updated the button enable logic in CollectionEditor.CollectionEditorCollectionForm.cs
  • Up button: Only enabled when SelectedIndex > 0 (not at first position)
  • Down button: Only enabled when SelectedIndex < Items.Count - 1 (not at last position)

Customer Impact

• Buttons now correctly reflect whether items can be moved up/down

Regression?

• No

Risk

• Minimal

Screenshots

Before

• When the first TabPage is selected:

  Up button should be disabled, but remains enabled.

  

• When the last TabPage is selected:

  Down button should be disabled, but remains enabled.

  

After

Selecting the first TabPage disables the Up button; Selecting the last TabPage disables the Down button

AfterChanges.mp4

Test methodology

• Manually

Test environment(s)

• .net 11.0.0-alpha.1.25617.103

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

This PR fixes a bug in the CollectionEditor dialog where the Up/Down buttons incorrectly remained enabled when the first or last item was selected. The fix adds position-based checks to ensure buttons are only enabled when items can actually be moved in the respective direction.

Key Changes:

• Enhanced button enable logic in UpdateEnabled() to check selected item position
• Up button now requires SelectedIndex > 0 (not at first position)
• Down button now requires SelectedIndex < Items.Count - 1 (not at last position)

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.01362%. Comparing base (01eefd4) to head (f2d183b).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #14163         +/-   ##
===================================================
- Coverage   77.15180%   76.01362%   -1.13818%     
===================================================
  Files           3279        3279                 
  Lines         645333      645333                 
  Branches       47720       47720                 
===================================================
- Hits          497886      490541       -7345     
- Misses        143754      145482       +1728     
- Partials        3693        9310       +5617     

Flag	Coverage Δ
Debug	76.01362% <0.00000%> (-1.13818%)	⬇️
integration	?
production	49.46327% <0.00000%> (-2.55080%)	⬇️
test	97.40559% <ø> (ø)
unit	49.46327% <0.00000%> (-0.00418%)	⬇️

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