[Exchange-Online][EWS][EWS-XML] Exchange server version "V2_22" returned for Office 365 breaks pattern - consequences?

Question

I just notice that talking to Office365 Exchange Web Services at https://outlook.office365.com/ews/exchange.asmx I get this in my SOAP response header:
<Envelope>
  <Header>
    <ServerVersionInfo MajorVersion="15" MinorVersion="0" MajorBuildNumber="1049" MinorBuildNumber="23" Version="V2_22"/>
  </Header>
This means that the Version 'schema version' property (http://msdn.microsoft.com/en-us/library/exchangewebservices.serverversioninfo.version%28v=exchg.150%29.aspx) now breaks the pattern of versions that we had earlier: Exchange2007, Exchange2007_SP1, Exchange2010,
Exchange2010_SP1, Exchange2010_SP2, Exchange2013
In the schema files I found through Google (searching for <xs:simpleType name="ExchangeVersionType">) I could not find anything later than <xs:enumeration value="Exchange2013"/> (e.g. at http://msdn.microsoft.com/en-us/library/ee237685%28v=exchg.80%29.aspx)
If I do a SOAP request with this "V2_22" string, I still get valid answers.
<soapenv:Envelope
  xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
  xmlns:typ="http://schemas.microsoft.com/exchange/services/2006/types"
  xmlns:mes="http://schemas.microsoft.com/exchange/services/2006/messages">
   <soapenv:Header>
      <typ:RequestServerVersion Version="V2_22"/>
   </soapenv:Header>
But it now looks as if the returned Version is no longer a reliable way to determine the Exchange server version. If V2_22 is not documented anywhere, who says it will not suddenly change to V2_23 tomorrow?
Question: Does this mean I will now have to change my version detection code to look at MajorVersion and then maintain a cross reference between MajorVersion and ExchangeVersionType **myself**? That is horrible: another dependency to maintain
is another potential code break.
As an aside: Note that the "Exchange Server Updates: build numbers and release dates" at http://technet.microsoft.com/en-us/library/hh135098%28v=exchg.150%29.aspx is no longer up to date, it does not mention the 15.0.1049.23 that my XML just returned

Answer 1

What really matters in EWS is the SchemaVersion as that will tell you what operations you can and can't use. From 2010 on you can use AutoDiscover to find what SchemaVersions are supported which is the best way to do version detection. eg
AutodiscoverService adAutoDiscoverService = new AutodiscoverService(ExchangeVersion.Exchange2010);
adAutoDiscoverService.Credentials = ncCred;
adAutoDiscoverService.EnableScpLookup = false;
adAutoDiscoverService.RedirectionUrlValidationCallback = adAutoDiscoCallBack;
adAutoDiscoverService.PreAuthenticate = true;
GetUserSettingsResponse adResponse = adAutoDiscoverService.GetUserSettings("[email protected]", (new UserSettingName[1] { UserSettingName.EwsSupportedSchemas }));
if (adResponse.Settings.Count >= 1)
String schemas = (String)adResponse.Settings[UserSettingName.EwsSupportedSchemas];
I would be careful using the Major build going forward if you have a look at the requests in OWA in Office365 you'll see they are using version 16 in cookies etc
Cheers
Glen