我正在编写一个C#应用程序，通过一些监控邮箱，清除超过指定期限（例如6个月）的电子邮件。

以前我要获取这些项，然后在foreach块中依次删除每个项。在寻找另一个问题的解决方案时，我无意中使用了DeleteItems。这需要System.Collection.Generic.IEnumerable，但在下面的代码中，FindItems返回System.Collection.ObjectModel.Collection。

如何转换或获取传递给DeleteItems的正确类型？

ExtendedPropertyDefinition allFoldersType = new ExtendedPropertyDefinition(13825, MapiPropertyType.Integer);

FolderId rootFolderId = new FolderId(WellKnownFolderName.Root);
FolderView folderView = new FolderView(1000);
folderView.Traversal = FolderTraversal.Deep;

SearchFilter.SearchFilterCollection searchFilterCollection = new SearchFilter.SearchFilterCollection(LogicalOperator.And);
searchFilterCollection.Add(new SearchFilter.IsEqualTo(allFoldersType, "2"));
searchFilterCollection.Add(new SearchFilter.IsEqualTo(FolderSchema.DisplayName, "allitems"));

FindFoldersResults findFoldersResults = exchangeService.FindFolders(rootFolderId, searchFilterCollection, folderView);

Folder allItemsFolder = findFoldersResults.Folders[0];

searchFilterCollection = new SearchFilter.SearchFilterCollection(LogicalOperator.And);
searchFilterCollection.Add(new SearchFilter.IsLessThanOrEqualTo(ItemSchema.DateTimeReceived, DateTime.Now.AddMonths(-6)));
searchFilterCollection.Add(new SearchFilter.IsEqualTo(ItemSchema.ItemClass, "IPM.Note"));

var findItems = allItemsFolder.FindItems(searchFilterCollection, new ItemView(100));
var items = findItems.Items;

exchangeService.DeleteItems(findItems, DeleteMode.HardDelete, SendCancellationsMode.SendToNone, AffectedTaskOccurrence.SpecifiedOccurrenceOnly);