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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.
Playlist boundary
AllStat already supplies the standard user-facing description for it; this custom block instead isolates the additional technical boundary. Earlier success in file lookup, network connection, parser creation or graph construction does not prove that the later the operation is valid.
Case-specific checkpoint: the preexisting value, attribute enumeration, code path that creates the attribute and object identity. The controlled comparison for it is: on a new playlist, add the attribute once and update its value through the supported setter rather than adding it again.
Closest distinction: An existing attribute is different from an item collision such as NS_E_WMP_PLAYLIST_EXISTS.
Evidence from the list model
| Capture | Why it matters for it |
|---|---|
| Object or resource | the preexisting value, attribute enumeration, code path that creates the attribute and object identity |
| State snapshot | Record the Player openState/playState or operation phase, object identity and exact timestamp when this result was returned. |
| First lower result | Keep the earliest Win32, Winsock, COM, parser, codec, DRM or device result that appears before this result. |
| Comparison record | Use one known-good case that follows the same API, protocol and component path while changing only the rejected precondition. |
Minimal playlist experiment
- Start from the original call and log
0xC00D106Ftogether with its object and operation phase. - Collect the preexisting value, attribute enumeration, code path that creates the attribute and object identity before changing the machine.
- 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.
- repeat on a fresh object if the original predates a configuration, device or resource change.
- validate the expected next operation, not just initial open or object creation.
What the result means
| Retest outcome | Interpretation |
|---|---|
| Same this result on the same object | The governing state or value is unchanged, or the caller is reusing an object created before the relevant change. |
| Fresh object succeeds | Lifetime, cached configuration or stale playlist/graph state contributed to this result. |
| A later HRESULT appears | The rejected condition — a caller attempted to add an attribute whose name is already present in the playlist metadata set — was cleared for it; diagnose the new code at its own layer. |
| Only one item or endpoint fails for it | The evidence favors resource-specific data, rights, routing or device state rather than a global Player failure. |
Actions that obscure the cause
- deleting the whole playlist to change one metadata field.
- Do not discard the first occurrence by repeatedly invoking Play, open, save or retry; later events can replace its original state.
- do not publish credentials, private URLs, license material or complete protected-content headers; retain only redacted identifiers, lengths, hashes and protocol fields.
Technical references
- Windows Media Player SDK
- Windows Media Playlists
- Windows Media Playlist elements
- Managing playlists
- Microsoft HRESULT registry
Retain before-and-after evidence for it so object recreation or content replacement is not mistaken for random retry success.
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