Question

将Exchange Web服务（EWS）托管API用于synchronize a folder hierarchy或synchronize items时，客户端缓存位于何处？它只在内存中吗？它在磁盘上吗？有没有办法找到或控制缓存的位置？我似乎无法在任何地方找到相关信息。

Answer 1

SyncFolderHierarchy和SyncFolderItems一起允许您有效地同步Exchange中邮箱中所有（或部分）文件夹的内容。

文章中指出的流程是指示性的。对SyncFolderItems的调用会返回ChangeCollection<T>，其中包含ItemChange或FolderChange类型的项目。如果您处理这些项目，则可以提取有关文件夹的其他信息，例如文件夹中每个项目的实际内容。

处理完ChangeCollection后，您应该在某处存储SyncState值。下次您致电SyncFolderItems时，您会传递该值，而Exchange会返回下一批商品。

由于可能（尤其是第一次同步）项目中的项目数量超过SyncFolderItems只能在一次通话中返回，因此您应该检查MoreChangesAvailable以确定是否还有其他操作。

所有这一切都变成了这个循环：

// Track whether there are more items available for download on the server.
bool moreChangesAvailable = false;
do {
    // Get a list of all items in the Inbox by calling SyncFolderHierarchy repeatedly until no more changes are available.
    // The folderId parameter must be set to the root folder to synchronize,
    // and must be same folder ID as used in previous synchronization calls. 
    // The propertySet parameter is set to IdOnly to reduce calls to the Exchange database,
    // because any additional properties result in additional calls to the Exchange database. 
    // The ignoredItemIds parameter is set to null, so that no items are ignored.
    // The maxChangesReturned parameter is set to return a maximum of 10 items (512 is the maximum).
    // The syncScope parameter is set to Normal items, so that associated items will not be returned.
    // The syncState parameter is set to cSyncState, which should be null in the initial call, 
    // and should be set to the sync state returned by the 
    // previous SyncFolderItems call in subsequent calls.
    ChangeCollection<ItemChange> icc = service.SyncFolderItems(new FolderId(WellKnownFolderName.Inbox), PropertySet.IdOnly, null, 10, SyncFolderItemsScope.NormalItems, cSyncState);

    // If the count of changes is zero, there are no changes to synchronize.
    if (icc.Count <> 0) {
        // Otherwise, write all the changes included in the response to the console. 
        foreach (ItemChange ic in icc) {
            Console.WriteLine("ChangeType: " + ic.ChangeType.ToString());
            Console.WriteLine("ItemId: " + ic.ItemId);
        }
    }

    // Save the sync state for use in future SyncFolderContent requests.
    // The sync state is used by the server to determine what changes to report
    // to the client.
    string sSyncState = icc.SyncState;

   // Determine whether more changes are available on the server.
   moreChangesAvailable = icc.MoreChangesAvailable;
}
while (moreChangesAvailable);

代码示例from MSDN，因为我不能说它比更好。

除非您选择自己存储客户端项目，否则不存在客户端缓存。如果你选择不存储它们，你可以简单地继续循环，直到你达到你感兴趣的东西开始的程度。例如，上面的代码不会下载任何内容，但每个项目的ItemChange记录和ID（由PropertySet.IdOnly表示）除外。

这MSDN article provides a great overview of the synchronization process。

EWS托管API同步缓存位置

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