StorageLibraryLastChangeId クラス

定義

名前空間:

Windows.Storage

特定の StorageFolder または StorageLibrary のインデックス作成サービスによって最後に処理された変更を表す一意の値に基づいて変更を追跡できます。

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

継承

Object Platform::Object IInspectable StorageLibraryLastChangeId

属性

ContractVersionAttribute MarshalingBehaviorAttribute ThreadingAttribute

Windows の要件

デバイス ファミリ	Windows 10, version 2104 (10.0.20348.0 で導入)
API contract	Windows.Foundation.UniversalApiContract (v12.0 で導入)

例

// 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();
    }
}
}

プロパティ

Unknown

USN ジャーナルがオーバーフローし、サービスが変更に対応できない場合、または変更 ID を計算できない別の理由がある場合に返されます。

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• Unknown