IWMPStringCollection2::getItemInfoByType method (wmp.h)

项目
4/26/2023

[The feature associated with this page, Windows Media Player SDK, is a legacy feature. It has been superseded by MediaPlayer. MediaPlayer has been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer instead of Windows Media Player SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The getItemInfoByType method retrieves the value corresponding to the specified string collection item index, name, language, and attribute index.

Syntax

HRESULT getItemInfoByType(
  [in]  long    lCollectionIndex,
  [in]  BSTR    bstrType,
  [in]  BSTR    bstrLanguage,
  [in]  long    lAttributeIndex,
  [out] VARIANT *pvarValue
);

Parameters

[in] lCollectionIndex

A long specifying the zero-based index of the string collection item from which to get the attribute.

[in] bstrType

BSTR containing the attribute name.

[in] bstrLanguage

BSTR containing the language. If the value is set to null or "" (empty string) the current locale string is used. Otherwise, the value must be a valid RFC 1766 language string such as "en-us".

[in] lAttributeIndex

A long containing the zero-based index of the attribute.

[out] pvarValue

Pointer to a VARIANT that receives the returned value.

Return value

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Return code	Description
S_OK	The method succeeded.

Remarks

This method supports attributes with multiple values and attributes with complex values. The getItemInfo method does not support attributes with multiple values or attributes with complex values.

By passing the value "ChildList" in the bstrType parameter, you can retrieve a new string collection that contains the children of one of the items in the parent string collection. For instance, if the parent collection contains a list of AlbumIDs, you can use this method to obtain a child string collection that contains all the tracks for one of the albums. This approach is faster and more efficient than calling the IWMPMediaCollection2::getStringCollectionByQuery method twice; once to get a collection of AlbumIDs, and a second time to get a collection of titles for a particular AlbumID. To use ChildList in the way just described, the parent string collection must be obtained from a media collection through IWMPLibraryServices, and not by using the IWMPCore::get_mediaCollection method.

When using ChildList, pass the value "ChildList" in the bstrType parameter, and the value 0 in the lAttributeIndex parameter. You can call QueryInterface on the VARIANT that is returned to obtain an IWMPStringCollection2 interface, from which you can access the child list.

To use this method, you must have read access to the library. For more information, see Library Access.

Windows Media Player 10 Mobile: This method is not supported.

Requirements


Minimum supported client	Windows Media Player 11.
Target Platform	Windows
Header	wmp.h
DLL	Wmp.dll

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