强制转换c#中的对象(将Exchange Web服务项转换为电子邮件)

我不知道如何做我需要做的事情。

我有一个名为"MarkAsRead"的方法，它接受ItemID，并且应该将邮件项目标记为已读。

但该项目似乎没有"IsRead"项目，只有一封电子邮件有，所以我需要将我的Exchange WebServices邮件项目转换为电子邮件。

这是代码：

尝试｛

            System.Diagnostics.Debugger.Break();
            //creates an object that will represent the desired mailbox
            Mailbox mb = new Mailbox(common.strInboxURL); 
            //creates a folder object that will point to inbox fold
            FolderId fid = new FolderId(WellKnownFolderName.Inbox, mb);
            //this will bind the mailbox you're looking for using your service instance
            Microsoft.Exchange.WebServices.Data.Folder inbox = Microsoft.Exchange.WebServices.Data.Folder.Bind(service, fid);
            //// if the property is not loaded yet, first load it
            //mail.Load(PropertySet(BasePropertySet.IdOnly, EmailMessageSchema.IsRead));
            //if (!mail.IsRead) // check that you don't update and create unneeded traffic
            //{
            //    mail.IsRead = true; // mark as read
            //    mail.Update(ConflictResolutionMode.AutoResolve); // persist changes
            //}
            // As a best practice, limit the properties returned to only those that are required.
            PropertySet propSet = new PropertySet(BasePropertySet.IdOnly, ItemSchema.Subject);
            // Bind to the existing item by using the ItemId.
            // This method call results in a GetItem call to EWS.
            Item item = Item.Bind(service, itemId, propSet);

            EmailMessage mail = Item.Bind(service, itemId, propSet);
            item.Load(new PropertySet(BasePropertySet.IdOnly,EmailMessageSchema.IsRead));
            item.IsRead = true;
            item.Update(ConflictResolutionMode.AlwaysOverwrite);
            return true;
        }

我正在尝试做这样的事情：

                // if the property is not loaded yet, first load it
            mail.Load(PropertySet(BasePropertySet.IdOnly, EmailMessageSchema.IsRead));
            if (!mail.IsRead) // check that you don't update and create unneeded traffic
            {
                mail.IsRead = true; // mark as read
                mail.Update(ConflictResolutionMode.AutoResolve); // persist changes
            }

不幸的是，我需要能够从该项目获得一个独特的电子邮件消息。

我该怎么做？

PropertySet propSet = new PropertySet(BasePropertySet.IdOnly, ItemSchema.Subject, EmailMessageSchema.IsRead);
EmailMessage mail = EmailMessage.Bind(service, itemId, propSet);
if (!mail.IsRead) // check that you don't update and create unneeded traffic
{
    mail.IsRead = true; // mark as read
    mail.Update(ConflictResolutionMode.AutoResolve); // persist changes
}

EmailMessage mail = Item.Bind(service, itemId, propSet) as EmailMessage;