好的，迄今为止我收到有关此主题的最佳信息是在此线程上： EWS-API-Create-Calendar-and-Share-with-reviewer-permissions。 我试图在该线程上提出这个问题，但实际上我将其发布为答案，因此被管理员删除了（我的错！）
免责声明：我是一名系统管理员，并在发展中月光...所以请原谅任何术语误用或用语混乱。
另外，请注意，我在这里使用C#。
我已经阅读了来自Microsoft的消息协议规范，并了解到某些扩展属性需要在消息项上创建以正确创建共享邀请对象。从上面提到的帖子中，我可以创建具有扩展属性的消息对象（SetExtendedProperty（extprop，value）确切地说）。 我了解到，我必须手动创建我正在设置的扩展属性，使用new ExtendedProperty()并在每个属性上填充正确的父GUID、HexID和Datatype。从我所了解的情况来看，这或多或少是由于API中没有内在的共享对象管理功能而需要采用的“解决方法”...
但我遇到了一些问题，需要进行澄清...
我想手动创建一个共享邀请（通过客户端，“用户”方式），然后附加到发送邀请的用户的“已发送邮件”中的消息。我希望枚举相对于我需要用来构建类似对象的所有可能属性，以便我可以将其用作模板并将我的对象属性与原始邀请进行比较。我可以很好地获取消息并查找许多属性，但没有任何“特殊”的属性。我能找到的唯一区分消息项的是它的IPM.Sharing项目类和它具有sharing_metadata.xml的附件。
但是，我正确地假设现在我们可以通过使用扩展属性通过API创建共享邀请，这并不意味着我们可以通过API读取这些属性吗？？
我尝试枚举扩展属性的一切都似乎行不通，并且总是返回什么都没有，而不是扩展属性数组。也许我做错了，但我想在花费数小时尝试实现不可能的事情之前问这个问题。
因此，如果我无法正确枚举扩展属性，是否有可能使用像ExFolders或MFCMAPI之类的东西来获取这些属性？？？
有什么想法/建议/批评吗？
谢谢！
更新：
这是我正在尝试为用户的日历文件夹创建共享邀请的函数...我已经评论了我被卡住的地方以及我并没有完全理解的地方：
public void CreateCalendarSharingRequest(string folderID, string owner, string sharedToUser)
{
// LOAD OUR CUSTOM PROPERTIES
Guid PropertySetSharing = new Guid("{00062040-0000-0000-C000-000000000046}");
Guid PropertySetInternetHeaders = new Guid("{00020386-0000-0000-C000-000000000046}");
// Sharing Properties
ExtendedPropertyDefinition PidLidSharingProviderGuid = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A01, MapiPropertyType.CLSID);
ExtendedPropertyDefinition PidLidSharingProvidorName = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A02, MapiPropertyType.String);
ExtendedPropertyDefinition PidLidSharingFlavor = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A18, MapiPropertyType.Integer);
ExtendedPropertyDefinition PidLidSharingRemoteStoreUid = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A48, MapiPropertyType.String);
ExtendedPropertyDefinition PidLidSharingRemoteUid = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A06, MapiPropertyType.String);
ExtendedPropertyDefinition PidTagMessageClass = new ExtendedPropertyDefinition(0x001A, MapiPropertyType.String);
ExtendedPropertyDefinition PidTagNormalizedSubject = new ExtendedPropertyDefinition(0x0E1D, MapiPropertyType.String);
ExtendedPropertyDefinition PidTagSubjectPrefix = new ExtendedPropertyDefinition(0x003D, MapiPropertyType.String);
ExtendedPropertyDefinition PidLidSharingCapabilities = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A17, MapiPropertyType.Integer);
ExtendedPropertyDefinition PidLidSharingInitiatorEntryId = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A09, MapiPropertyType.Binary);
ExtendedPropertyDefinition PidLidSharingConfigurationUrl = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A24, MapiPropertyType.String);
ExtendedPropertyDefinition PidLidSharingInitiatorName = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A07, MapiPropertyType.String);
ExtendedPropertyDefinition PidLidSharingInitiatorSMTP = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A08, MapiPropertyType.String);
ExtendedPropertyDefinition PidLidSharingLocalType = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A14, MapiPropertyType.String);
ExtendedPropertyDefinition PidLidSharingRemoteType = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A1D, MapiPropertyType.String);
ExtendedPropertyDefinition PidLidSharingRemoteName = new ExtendedPropertyDefinition(PropertySetSharing, 0x8A05, MapiPropertyType.String);
// Internet Header Properties
ExtendedPropertyDefinition PidNameContentClass = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "Content-Class", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingCapabilities = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Capabilities", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingConfigUrl = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Config-Url", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingFlavor = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Flavor", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingLocalType = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Local-Type", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingRemoteName = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Remote-Name", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingRemoteStoreUid = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Remote-Store-Uid", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingRemoteType = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Remote-Type", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingRemoteUid = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Remote-Uid", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingProviderGuid = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Provider-Guid", MapiPropertyType.String);
ExtendedPropertyDefinition PidNameXSharingProviderName = new ExtendedPropertyDefinition(PropertySetInternetHeaders, "X-Sharing-Provider-Name", MapiPropertyType.String);
// Bind to the web services and currently selected folder
// Get the current list of delegates for this folder
ExchangeService service = GetExchangeService();
// Create a new message
EmailMessage invitationRequest = new EmailMessage(service);
invitationRequest.Subject = "I'd like to share my calendar with you";
invitationRequest.Body = "Send by Exchange Administrator on behalf of user";
invitationRequest.From = GetSMTPAddress(owner);
invitationRequest.ItemClass = "IPM.Sharing";
invitationRequest.SetExtendedProperty(PidNameContentClass, "Sharing");
invitationRequest.SetExtendedProperty(PidTagMessageClass, "IPM.Sharing");
invitationRequest.SetExtendedProperty(PidLidSharingFlavor,0x20310); /* Indicates Invitation for a special folder */
invitationRequest.SetExtendedProperty(PidNameXSharingFlavor, "20310"); /* Text representation of SharingFlavor value */
invitationRequest.SetExtendedProperty(PidLidSharingProviderGuid, PropertySetSharing.ToString());
invitationRequest.SetExtendedProperty(PidNameXSharingProviderGuid, PropertySetSharing.ToString());
invitationRequest.SetExtendedProperty(PidLidSharingCapabilities, 0x40290); /* value for Special Folders */
invitationRequest.SetExtendedProperty(PidNameXSharingCapabilities, "40290"); /* Test representation of SharingCapabilities value */
// THIS IS WHERE IM STUCK - I understand how to set some of the properties like above, but then
// it starts needing the entryID properties for the folder being shared, etc...and I'm not entirely
// sure which properties I have to set and how many can/will be autopopulated by the transport provider
// All i wanna do is send an invite message for sharing the calendar folder from one user to another!
// Add recipient info
//invitationRequest.ToRecipients.Add(sharedToUser);
//invitationRequest.SendAndSaveCopy();
}