使用.NET讀取exchange郵件

公司有個第3方的系統，不能操作源碼修改錯誤捕獲，但是錯誤會發一個郵件出來，里面包含了主要的信息。於是想從郵件下手，提取需要的數據

開始考慮使用的是exchange service，主要參考http://blog.csdn.net/tider_ys/article/details/6637879

中間遇到幾個問題，稍微記錄一下：

1. The request failed with HTTP status 401: Unauthorized XXXX。添加web service的時候，使用的地址應該是 https://<server name>/EWS/Services.wsdl 這種形式，但是在給ExchangeServiceBinding.Url賦值，然后連接exchange servervice的時候，報錯。通過程序call service，使用的地址 https://<server name>/EWS/Exchange.asmx

http://www.windows-server-answers.com/microsoft/Exchange-Development/30599015/the-request-failed-with-http-status-405-method-not-allowed.aspx

2. The remote certificate is invalid according to the validation procedure。建立連接時報錯，稍微添加一點點代碼

ServicePointManager.ServerCertificateValidationCallback = (obj, certificate, chain, errors) => true;

https://social.msdn.microsoft.com/Forums/en-US/98aa34b2-69b5-4b8a-8f77-2a3f08869e3b/the-remote-certificate-is-invalid-according-to-the-validation-procedure?forum=exchangesvrdevelopment

關於exchange webservice，可以參考http://msdn.microsoft.com/en-us/library/office/exchangewebservices(v=exchg.150).aspx

做到后來發現，如果直接使用exchange service，需要一步步查找郵件文件夾，搜索郵件，獲取郵件內容，代碼寫起來也有點亂，不是很容易懂。參考資料也比較少，比如我要查收件箱下的一個文件夾test，需要FolderId，但這個值怎么取還挺麻煩，看到的代碼大部分都是遍歷子文件夾，然后比較名字。剛好在這個過程中，發現微軟已經提供了新的API來操作exchange，EWS Managed API

Working with the EWS Managed API 2.0

看了一些sample之后，這個API要比直接訪問web service方便得多，操作方式簡單易懂，代碼也更簡潔，可讀性更好。而且，還是開源的https://github.com/OfficeDev/ews-managed-api

要連接exchange server，不再需要指定url，而是可以通過ExchangeService.AutodiscoverUrl

public ExchangeService GetService()
{
    ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010);

    service.Credentials = new NetworkCredential("[e-mail]", "test");

    service.AutodiscoverUrl("[e-mail]", RedirectionUrlValidationCallback);

    return service;
}

用代碼來說話，查找收件箱中的子文件夾"Test Service"，查找文件夾中標題為"Test email"且發送時間在2014/11/28之后的郵件

private void CheckEmail()
{
    ExchangeService service = GetService();

    //find sub folder in inbox
    FolderId folder = FindFolderIdByDisplayName(service, "Test Service", WellKnownFolderName.Inbox);

    //prepare search filter
    List<SearchFilter> searchFilterCollection = new List<SearchFilter>();

    //subject filter
    searchFilterCollection.Add(new SearchFilter.ContainsSubstring(ItemSchema.Subject, "Test email"));

    //date time received filter
    DateTime lastProcessedTime = new DateTime(2014, 11, 28, 0, 0, 0);
    searchFilterCollection.Add(new SearchFilter.IsGreaterThan(ItemSchema.DateTimeSent, lastProcessedTime));

    //operator: and
    SearchFilter searchFilter = new SearchFilter.SearchFilterCollection(LogicalOperator.And, searchFilterCollection.ToArray());

    int offset = 0;
    int pageSize = 20;
    bool MoreItems = true;

    //search in pages
    while (MoreItems)
    {
        ItemView view = new ItemView(pageSize, offset, OffsetBasePoint.Beginning);
        view.PropertySet = new PropertySet(BasePropertySet.IdOnly, ItemSchema.Subject, ItemSchema.DateTimeReceived);
        view.OrderBy.Add(ItemSchema.DateTimeReceived, SortDirection.Ascending);
        FindItemsResults<Item> findResults = service.FindItems(folder, searchFilter, view);
        foreach (Item myItem in findResults.Items)
        {
            //body message does not include in returned properties, get message details
            Item item = Item.Bind(service, myItem.Id);
            //Process(item);
        }

        //last page
        if (!findResults.MoreAvailable)
            MoreItems = false;

        //next page
        if (MoreItems)
            offset += pageSize;
    }
}

可以看到整個代碼比直接訪問web service簡潔不少，更容易理解

微軟官方實例代碼下載：https://code.msdn.microsoft.com/Exchange-2013-101-Code-3c38582c