unoplatform/uno · error · InvalidOperationException

Unsupported media source type

Error message

Unsupported media source type

What it means

InvalidOperationException thrown in InitializeSource (WebAssembly) when _owner.Source is not null but is none of MediaPlaybackList, MediaPlaybackItem, or MediaSource. The WASM media extension only supports those three source types; any other IMediaPlaybackSource implementation falls into the default case.

Source

Thrown at src/AddIns/Uno.UI.MediaPlayer.WebAssembly/MediaPlayerExtension.cs:323

					{
						_uri = _playlistItems[0];
					}
					else
					{
						throw new InvalidOperationException("Playlist Items could not be set");
					}
					break;

				case MediaPlaybackItem item:
					_uri = item.Source.Uri;
					break;

				case MediaSource source:
					_uri = source.Uri;
					break;

				default:
					throw new InvalidOperationException("Unsupported media source type");
			}

			ApplyVideoSource();
			Events?.RaiseSourceChanged();
		}
		catch (global::System.Exception ex)
		{

			this.Log().Debug($"MediaPlayerElementExtension.InitializeSource({ex.Message})");
			OnMediaFailed(ex);
		}
	}

	public void ReInitializeSource()
	{
		NaturalDuration = TimeSpan.Zero;
		if (Position != TimeSpan.Zero)
		{

View on GitHub (pinned to 0418340488)

Solutions

1. Use one of the supported source types: MediaPlaybackList, MediaPlaybackItem, or MediaSource.
2. Wrap custom sources in a MediaSource via MediaSource.CreateFromUri / CreateFromStream before assignment.
3. Upgrade Uno.UI.MediaPlayer.WebAssembly to match the Uno.UI version so newer source types are handled.
4. Log _owner.Source.GetType() before assignment to identify unsupported types in development.

Example fix

// before — unsupported source type
player.Source = myCustomSource;

// after — wrap in a supported type
player.Source = MediaSource.CreateFromUri(myCustomSource.Uri);

// Ensure source is one of the three supported types
var src = player.Source;
if (src is MediaPlaybackList or MediaPlaybackItem or MediaSource)
    extension.InitializeSource();
else
    Log.Error($"Unsupported source type: {src?.GetType()}");

bool IsSupportedMediaSource(object? src)
    => src is MediaPlaybackList or MediaPlaybackItem or MediaSource;

try { extension.InitializeSource(); }
catch (InvalidOperationException ex) when (ex.Message.Contains("Unsupported media source type"))
{ Log.Error($"Unsupported source: {player.Source?.GetType()}"); OnMediaFailed(ex); }

When it happens

Trigger: Assigning MediaPlayer.Source to a custom IMediaPlaybackSource implementation, a future/new source type not yet handled, or an object that is not one of the three supported concrete types. (A null Source returns early before the switch, so this is strictly an unrecognized non-null source.)

Common situations: Using a custom IMediaPlaybackSource; a version mismatch where a newer WinUI source type is passed to an older WASM extension; assigning an arbitrary object to Source.

Related errors

• MediaPlayerPresenterExtension must be initialized with a Med
• Playlist Items could not be set
• IStorageFile is not supported
• IMediaSource is not supported
• IRandomAccessStream is not supported

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/0014f6f446635940. Report an issue: GitHub.