使用.NET读取exchange邮件

公司有个第3方的系统，不能操作源码修改错误捕获，但是错误会发一个邮件出来，里面包含了主要的信息。于是想从邮件下手，提取需要的数据

开始考虑使用的是exchange service，主要参考http://blog.csdn.net/tider_ys/article/details/6637879

中间遇到几个问题，稍微记录一下：

1. The request failed with HTTP status 401: Unauthorized XXXX。添加web service的时候，使用的地址应该是 https://<server name>/EWS/Services.wsdl 这种形式，但是在给ExchangeServiceBinding.Url赋值，然后连接exchange servervice的时候，报错。通过程序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。建立连接时报错，稍微添加一点点代码

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

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

做到后来发现，如果直接使用exchange service，需要一步步查找邮件文件夹，搜索邮件，获取邮件内容，代码写起来也有点乱，不是很容易懂。参考资料也比较少，比如我要查收件箱下的一个文件夹test，需要FolderId，但这个值怎么取还挺麻烦，看到的代码大部分都是遍历子文件夹，然后比较名字。刚好在这个过程中，发现微软已经提供了新的API来操作exchange，EWS Managed API

Working with the EWS Managed API 2.0

看了一些sample之后，这个API要比直接访问web service方便得多，操作方式简单易懂，代码也更简洁，可读性更好。而且，还是开源的https://github.com/OfficeDev/ews-managed-api

要连接exchange server，不再需要指定url，而是可以通过ExchangeService.AutodiscoverUrl

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

    service.Credentials = new NetworkCredential("test@test.com", "test");

    service.AutodiscoverUrl("test@test.com", RedirectionUrlValidationCallback);

    return service;
}

用代码来说话，查找收件箱中的子文件夹"Test Service"，查找文件夹中标题为"Test email"且发送时间在2014/11/28之后的邮件

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;
    }
}

可以看到整个代码比直接访问web service简洁不少，更容易理解

微软官方实例代码下载：https://code.msdn.microsoft.com/Exchange-2013-101-Code-3c38582c