Problem

1. Drawing Renaming: Renaming an ExcelDrawing updated the underlying XML but failed to synchronize the change with the parent's _drawingNames lookup dictionary. This caused subsequent lookups and Remove() calls on renamed drawings to fail with a KeyNotFoundException.
2. Group Shape Removal: ExcelDrawingsGroup.Remove() removed drawings from the internal list but did not clean up their entries from the _drawingNames dictionary or re-index the remaining shapes, causing index desynchronization.
3. Case Sensitivity: The _drawingNames dictionary in ExcelDrawingsGroup was case-sensitive, unlike the worksheet-level dictionary which is case-insensitive, resulting in inconsistent behavior.

Solution

• Synchronized Renaming: Updated the ExcelDrawing.Name setter to validate uniqueness across both worksheet and group-level collections first, then update both lookup dictionaries.
• Group Shape Re-indexing: Fixed ExcelDrawingsGroup.Remove to remove the shape's name from _drawingNames and re-index the shifted indices of the remaining drawings in the group.
• Case-Insensitive Group Lookup: Initialized _drawingNames in ExcelDrawingsGroup with StringComparer.OrdinalIgnoreCase to align with worksheet-level drawing lookups.

Testing

Added unit tests in DrawingTest.cs to verify renaming and removal behavior for both standard and grouped drawings:

• DrawingNameChangeAndRemovalTest
• GroupedDrawingNameChangeAndRemovalTest