Windows Media Player 11 SDK Playlist Attributes 

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Playlist Attributes

Playlists have metadata information called attributes, just as media items have attributes. You can retrieve the names and values of playlist attributes and display them in your user interface, or your code can take actions based on the value of an attribute.

Playlists are defined in files organized in an XML format, and particular elements in the file define playlist attributes. Some attribute elements are well-known; the author of the metafile can also define arbitrary attributes. For more information about attribute elements in playlist files, see Retrieving Metadata.

The library may provide additional playlist attributes, such as SourceURL or UserLastPlayedTime. For more information about the library playlist attributes, see the Windows Media Player Attribute Reference.

The Playlist**.attributeCount** property retrieves the number of attributes associated with the playlist. The Playlist**.attributeName** property retrieves the name of an attribute based on its index, and the Playlist**.getItemInfo** method retrieves the value of an attribute based on its name.

You can modify the value of an attribute of the current playlist with the Playlist**.setItemInfo** method.

A special use of the setItemInfo method is to sort the items in the playlist, using the SortAttribute attribute. The following C# example sorts a playlist by the values of the UserLastPlayedTime attribute. The variable Playlist is a reference to a Playlist object.

Playlist.setItemInfo("SortAttribute", "UserLastPlayedTime");

Throughout this topic, the Player object was defined in the following manner:

AxWMPLib.AxWindowsMediaPlayer Player;
using WMPLib;

The following C# example code demonstrates retrieving playlist attributes. The first function, ShowPlaylists, populates a ListBox control with the names of the available playlists. The second part is the list box event handler. When the user clicks a playlist name, this code retrieves the attributes for that playlist and displays those attributes in a second list box.

// Member variables
IWMPPlaylistCollection PlaylistColl;
IWMPPlaylistArray PlaylistArray;

private void ShowPlaylists()
{
    // Retrieve the playlist collection
    PlaylistColl = Player.playlistCollection;
    // Store the collection in a playlist array
    PlaylistArray = PlaylistColl.getAll();

    // Retrieve the count of elements
    iCount = PlaylistArray.count;

    // Update the list box with the playlist names.
    lstPlaylist.BeginUpdate();
    for (int i=0; i<iCount; i++)
    {
        lstPlaylist.Items.Add(PlaylistArray.Item(i).name);
    }
    lstPlaylist.EndUpdate();

    // Set the selected index to zero
    lstPlaylist.SelectedIndex = 0;
}

The SelectedIndexChanged event for the ListBox control is called each time the user selects a playlist name. The following event handler fills a second list box with the attribute names and values corresponding to the user's selection.

private void lstPlaylist_SelectedIndexChanged(object sender, System.EventArgs e)
{
    IWMPPlaylist Playlist = PlaylistArray.Item(lstPlaylist.SelectedIndex);
    string strAttr="";
    string strItemNames="";
    int iAttribCount=0;

    iAttribCount = Playlist.attribCount;
    for (j=0; j<iAttribCount; j++)
    {
        strAttr=Playlist.get_attributeName(j) + " -- ";
        strAttr+=Playlist.getItemInfo(Playlist.get_attributeName(j));
        lstOutput.Items.Add(strAttr);
    }
}

See Also

• Managing Playlists
• Media Item Attributes
• Playlist Object

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