c# - EWS FindItemsResults Item.Move() 不会将某些项目类型移动到邮件文件夹，例如 IPM.Appointment

Question

我有一些代码可以将项目从已删除项目移动到邮件文件夹中。该代码运行良好并且通常移动所有项目。当它遇到一个不是 IPM 的项目时，就会出现问题。请注意。它给出的错误是空引用(参见:What is a NullReferenceException, and how do I fix it?)

这很奇怪，因为那里有项目而且它不能为空。

这是一段代码摘录:

// Specify the Exchange Service
ExchangeService E_SERVICE = new ExchangeService(ExchangeVersion.Exchange2010_SP2);

// Look at the root of the Mailbox (Top of Information Store)
FolderId fldr_id = WellKnownFolderName.MsgFolderRoot;

// Define the folder view
FolderView newFV = new FolderView(1000);

// Perform a deep traversal
newFV.Traversal = FolderTraversal.Deep;

// Get the results of all the folders in the Mailbox
FindFoldersResults f_results = E_SERVICE.FindFolders(fldr_id, newFV);

// Define the source and target folder id variables as null.
FolderId src_fldr_id = null;
FolderId tgt_fldr_id = null;

// Define the folders we are looking to move items from the source to the target
string source = "Deleted Items"
string target = "Old Deleted Items"

// Search through all the folders found in the mailbox
foreach (Folder fldr in f_results)
{
    // If the source folder name is the same as the current folder name then set the source folder ID
    if (fldr.DisplayName.ToLower() == source.ToLower())
    {
        src_fldr_id = fldr.Id;
    }
    // If the target folder name is the same as the current folder name then set the target folder ID
    if (fldr.DisplayName.ToLower() == target.ToLower())
    {
        tgt_fldr_id = fldr.Id;
    }
}

// Get all the items in the folder
FindItemsResults<Item> findResults = E_SERVICE.FindItems(src_fldr_id, new ItemView(1000));

// If the number of results does not equal 0
if (findResults.TotalCount != 0)
{
    // For each item in the folder move it to the target folder located earlier by ID.
    foreach(Item f_it in findResults)
    {
        f_it.Move(tgt_fldr_id);
    }
}

我们在以下行中抛出错误:

        f_it.Move(tgt_fldr_id);

这是一个空引用异常，不可能是这种情况，因为那里有项目，而且通常是不是 IPM 的项目。注意。

那么我将如何解决这个问题并确保无论元素是什么类型都能移动？

我之前已经在这里发布过关于这个 Unable to move Mail items of different Item classes from the same folder using EWS 的信息

只有在实际情况并非如此时才被驳斥为 NullReferenceException!

因此，我们将不胜感激任何有帮助的答案。

Answer 1

好吧，解决这个问题的方法是确保在执行 Move() 之前先 Load() 项目

确保使用 try..catch block 并像下面这样处理异常:

try
{
    f_it.Move(tgt_fldr_id);
}
catch (Exception e)
{
    Item draft = Item.Bind(E_SERVICE, f_it.Id);
    draft.Load();
    draft.Move(tgt_fldr_id);
}

这将强制项目单独加载然后移动它，即使它抛出错误也是如此。为什么，它这样做还不知道。但应该希望能帮助那些苦苦挣扎的人为什么会收到 NullReferenceException

谢谢大家!

编辑:您可能想阅读 https://social.msdn.microsoft.com/Forums/exchange/en-US/b09766cc-9d30-42aa-9cd3-5cf75e3ceb93/ews-managed-api-msgsender-is-null?forum=exchangesvrdevelopment为什么某些项目为 Null，因为这将帮助您更好地处理返回的 Null 项目。