What does HRESULT 0xC00D106F (NS_E_WMX_ATTRIBUTE_ALREADY_EXISTS) mean?

NS_E_WMX_ATTRIBUTE_ALREADY_EXISTS

Understanding NS_E_WMX_ATTRIBUTE_ALREADY_EXISTS in a Windows Media playlist

NS_E_WMX_ATTRIBUTE_ALREADY_EXISTS (0xC00D106F) is returned when a caller attempted to add an attribute whose name is already present in the playlist metadata set.

Distinguish in-memory Playlist state, WPL or ASX parsing, nested-list expansion, Media-object resolution and execution of referenced items. Record what the Player had already completed because later retries often replace the original evidence. The specific rejected condition is a caller attempted to add an attribute whose name is already present in the playlist metadata set.

Minimal playlist experiment

1. Start from the original call and log 0xC00D106F together with its object and operation phase.
2. Collect the preexisting value, attribute enumeration, code path that creates the attribute and object identity before changing the machine.
3. Use this single-variable test: on a new playlist, add the attribute once and update its value through the supported setter rather than adding it again.
4. Repeat on a fresh object if the original predates a configuration, device or resource change.
5. Validate the expected next operation, not just initial open or object creation.

What the result means

Actions that obscure the cause

• deleting the whole playlist to change one metadata field.

Technical references

• Windows Media Player SDK
• Windows Media Playlists
• Windows Media Playlist elements
• Managing playlists
• Microsoft HRESULT registry