StorageLibraryLastChangeId Kelas

Referensi

Definisi

Ruang nama:: Windows.Storage

Penting

Beberapa informasi terkait produk prarilis yang dapat diubah secara signifikan sebelum dirilis. Microsoft tidak memberikan jaminan, tersirat maupun tersurat, sehubungan dengan informasi yang diberikan di sini.

Edit

Memungkinkan Anda melacak perubahan berdasarkan nilai unik yang mewakili perubahan terakhir yang diproses oleh layanan pengindeksan untuk StorageFolder atau StorageLibrary yang diberikan.

public ref class StorageLibraryLastChangeId sealed

/// [Windows.Foundation.Metadata.ContractVersion(Windows.Foundation.UniversalApiContract, 720896)]
/// [Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
/// [Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
class StorageLibraryLastChangeId final

[Windows.Foundation.Metadata.ContractVersion(typeof(Windows.Foundation.UniversalApiContract), 720896)]
[Windows.Foundation.Metadata.MarshalingBehavior(Windows.Foundation.Metadata.MarshalingType.Agile)]
[Windows.Foundation.Metadata.Threading(Windows.Foundation.Metadata.ThreadingModel.Both)]
public sealed class StorageLibraryLastChangeId

Public NotInheritable Class StorageLibraryLastChangeId

Warisan: Object Platform::Object IInspectable StorageLibraryLastChangeId

Atribut: ContractVersionAttribute MarshalingBehaviorAttribute ThreadingAttribute

Persyaratan Windows

Rangkaian perangkat	Windows 10, version 2104 (diperkenalkan dalam 10.0.20348.0)
API contract	Windows.Foundation.UniversalApiContract (diperkenalkan dalam v12.0)

Contoh

// applications are expected to persist the previous value
UINT64 appsLastPersistedChangeId = StorageLibraryLastChangeId::Unknown();
StorageFolder folder = StorageFolder::GetFolderFromPathAsync(L"my folder path").get();

StorageLibraryChangeTracker tracker = folder.TryGetChangeTracker();
if (tracker != nullptr)
{
StorageLibraryChangeTrackerOptions ops;
ops.TrackChangeDetails(false);
tracker.Enable(ops);

StorageLibraryChangeReader reader = tracker.GetChangeReader();
if (reader != nullptr)
{
    UINT32 changeId = reader.GetLastChangeId();
    if ((changeId == StorageLibraryLastChangeId::Unknown())
    {
        ScanFolderSlow();
    }
    else if (changeId == 0)
    {
        // no changes in the storage folder yet, OR nothing has changed
        ProcessNormalApplicationStartup();
    }
    else if (changeId != appsLastPersistedChangeId)
    {
        // There have been new changes since we’ve last ran, process them
        appsLastPersistedChangeId = changeId;
        ScanFolderForChanges();
    }
    else
    {
        // changeId and our last persisted change id match, also normal application startup
        ProcessNormalApplicationStartup();
    }
}
}

Properti

Unknown

Dikembalikan ketika jurnal USN meluap dan layanan tidak dapat mengikuti perubahan atau ada alasan lain id perubahan tidak dapat dihitung.

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Lihat juga

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