Exchange Web Services - Get list of all available "ExtendedProperty"
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I have an Exchange Server that contains items with custom fields (e.g. Contacts and Events with custom ExtendedProperty values). I am looking for a way to display these fields using Exchange Web Services (EWS). 

According to the [Microsoft documentation][1], there's a simple way to retrieve individual ExtendedProperty values using the FindItem method. Example:

    <?xml version="1.0" encoding="utf-8"?>
    <soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages"
         xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types"
         xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
      <soap:Header>
        <t:RequestServerVersion Version="Exchange2010" />
      </soap:Header>
      <soap:Body>
        <m:FindItem Traversal="Shallow">
          <m:ItemShape>
            <t:BaseShape>AllProperties</t:BaseShape>
            <t:AdditionalProperties>
              <t:ExtendedFieldURI PropertySetId="c11ff724-aa03-4555-9952-8fa248a11c3e" 
                 PropertyName="Expiration Date" PropertyType="String" />
            </t:AdditionalProperties>
          </m:ItemShape>
          <m:IndexedPageItemView MaxEntriesReturned="10" Offset="0" BasePoint="Beginning" />
          <m:ParentFolderIds>
            <t:DistinguishedFolderId Id="inbox" />
          </m:ParentFolderIds>
        </m:FindItem>
      </soap:Body>
    </soap:Envelope> 


However, this requires the PropertySetID along with the PropertyType and PropertyName. In my case, I have no idea what PropertySetIDs are available, much less the PropertyType and PropertyName. Is there a way to get a list of all available Extended Properties?


  [1]: http://msdn.microsoft.com/en-us/library/exchange/dd633697%28v=exchg.80%29