windows-8 – 在winrt中访问文件时出现一些异常

问题1：

var file = await StorageFile.GetFileFromPathAsync(filePath);

有时,GetFileFromPathAsync将抛出“rpc服务器不可用”异常.

问题2：

MusicProperties musicProp = await file.Properties.GetMusicPropertiesAsync();

有时它会引发异常：

Unable to cast COM object of type 'Windows.Storage.FileProperties.MusicProperties' to interface type 'Windows.Storage.FileProperties.IMusicProperties'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{BC8AAB62-66EC-419A-BC5D-CA65A4CB46DA}' failed due to the following error: The application called an interface that was marshalled for a different thread. (Exception from HRESULT: 0x8001010E (RPC_E_WRONG_THREAD)).

问题3：

QueryOptions query = new QueryOptions(CommonFileQuery.OrderByMusicInfo,extensionList);
StorageFileQueryResult queryResult = folder.CreateFileQueryWithOptions(query);
IReadOnlyList<IStorageFile> files = await queryResult.GetFilesAsync();

有时会抛出异常：

Unable to cast COM object of type 'Windows.Storage.StorageFile' to interface type 'Windows.Storage.IStorageFile'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{C7034384-F12E-457A-89DA-69A5F8186D1C}' failed due to the following error: The application called an interface that was marshalled for a different thread. (Exception from HRESULT: 0x8001010E (RPC_E_WRONG_THREAD)).

这些异常不会一直抛出,但有时会抛出.为什么？