How to: Work with hidden folders
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How to: Work with hidden folders by using EWS in Exchange

Exchange

Learn how to make a folder hidden and find hidden folders by using the EWS Managed API or EWS in Exchange.

Last modified: March 09, 2015

Applies to: EWS Managed API | Exchange Online | Exchange Server 2013 | Office 365

In this article
Hide a folder by using the EWS Managed API
Hide a folder by using EWS
Find all hidden folders by using the EWS Managed API
Find all hidden folders by using EWS
Next steps
Additional resources

With one exception, folders in the root of an Exchange mailbox (the non-IPM subtree) are hidden from the user. Conversely, all folders in the MsgFolderRoot (the IPM subtree) are visible to the user. So how do you hide a folder under the MsgFolderRoot? It's not that tricky — it comes down to just one property, the PidTagAttributeHidden (0x10F4000B) extended property. When this property is set to true, Outlook or another client that uses the property to determine folder visibility will hide the folder from the user's view. Because this is an extended property, it’s more complex to use than your average folder property, so this article will walk you through the main scenarios.

Table 1.  EWS Managed API methods and EWS operations for working with hidden folders

Task

EWS Managed API method

EWS operation

Hide a folder

Folder.Bind followed by Folder.Update

GetFolder followed by UpdateFolder

Find hidden folders

FindFolders

FindFolder

Are you wondering what the one exception is — that is, what folder in the root IS visible to users? It's the Finder folder (also known as the SearchFolders WellKnownFolder enumeration value, or the searchfolders DistinguishedFolderId element value), which contains users’ search folders. Search folders created in the Finder folder are visible to Outlook users. If you need to create a search folder that is not visible to users, move it under the root folder to hide it. Unlike for other folders, setting the PidTagAttributeHidden property to true will not hide a search folder in the Finder folder.

You can make an existing folder a hidden folder by changing the PidTagAttributeHidden extended property to true. First, create an extended property definition for the property. Next, use the Bind method to get to the folder, then update the value of the PidTagAttributeHidden property to true, and use the Update method to save the changes.

This example assumes that service is a valid ExchangeService object for the mailbox owner, that the user has been authenticated to an Exchange server, and that folderId is a valid Folder.Id that identifies the folder to hide.

private static void MakeHidden(FolderId folderId, ExchangeService service)
{
    // Create an extended property definition for the PidTagAttributeHidden property.
    ExtendedPropertyDefinition isHiddenProp = new ExtendedPropertyDefinition(0x10f4, MapiPropertyType.Boolean);
    PropertySet propSet = new PropertySet(isHiddenProp);

    // Bind to a folder and retrieve the PidTagAttributeHidden property.
    Folder folder = Folder.Bind(service, folderId, propSet);

    // Set the PidTagAttributeHidden property to true.
    folder.SetExtendedProperty(isHiddenProp, true);

    // Save the changes.
    folder.Update();
}

You can use EWS to make an existing folder a hidden folder by changing the PidTagAttributeHidden extended property to true. First, use the GetFolder operation to get to the folder, then retrieve the PidTagAttributeHidden property by including the ExtendedFieldURI element, and setting the PropertyTag value to 4340 and the PropertyType value to Boolean.

This is also the XML request that the EWS Managed API sends when you use the Bind method to get a folder before making it a hidden folder.

The FolderId value is shortened for readability.

<?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="Exchange2007_SP1" />
  </soap:Header>
  <soap:Body>
    <m:GetFolder>
      <m:FolderShape>
        <t:BaseShape>IdOnly</t:BaseShape>
        <t:AdditionalProperties>
          <t:ExtendedFieldURI PropertyTag="4340"
                              PropertyType="Boolean" />
        </t:AdditionalProperties>
      </m:FolderShape>
      <m:FolderIds>
        <t:FolderId Id="IQywAAAA==" />
      </m:FolderIds>
    </m:GetFolder>
  </soap:Body>
</soap:Envelope>

The server responds to the GetFolder request with a GetFolderResponse message that includes a ResponseCode element value of NoError, which indicates that the folder was retrieved successfully. The response also includes a Value for the ExtendedProperty. In this example, the Value is set to false, which means that the folder is currently not hidden.

<?xml version="1.0" encoding="utf-8"?>
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header>
    <h:ServerVersionInfo MajorVersion="15"
                         MinorVersion="0"
                         MajorBuildNumber="898"
                         MinorBuildNumber="23"
                         Version="V2_10"
                         xmlns:h="http://schemas.microsoft.com/exchange/services/2006/types"
                         xmlns="http://schemas.microsoft.com/exchange/services/2006/types"
                         xmlns:xsd="http://www.w3.org/2001/XMLSchema"
                         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" />
  </s:Header>
  <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <m:GetFolderResponse xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages"
                         xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types">
      <m:ResponseMessages>
        <m:GetFolderResponseMessage ResponseClass="Success">
          <m:ResponseCode>NoError</m:ResponseCode>
          <m:Folders>
            <t:Folder>
              <t:FolderId Id="IQywAAAA=="
                          ChangeKey="AQAAABYAAAD32nSTjepyT63rYH17n9THAAAAABED" />
              <t:ExtendedProperty>
                <t:ExtendedFieldURI PropertyTag="0x10f4"
                                    PropertyType="Boolean" />
                <t:Value>false</t:Value>
              </t:ExtendedProperty>
            </t:Folder>
          </m:Folders>
        </m:GetFolderResponseMessage>
      </m:ResponseMessages>
    </m:GetFolderResponse>
  </s:Body>
</s:Envelope>

To change the value of the ExtendedProperty to true, use the UpdateFolder operation. Include the ExtendedProperty, ExtendedFieldURI, and Value elements for the PidTagAttributeHidden extended property, and set the Value element to true to hide the folder.

This is also the XML request that the EWS Managed API sends when you use the Update method to update a folder to make it a hidden folder.

<?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="Exchange2007_SP1" />
  </soap:Header>
  <soap:Body>
    <m:UpdateFolder>
      <m:FolderChanges>
        <t:FolderChange>
          <t:FolderId Id="IQywAAAA=="
                      ChangeKey="AQAAABYAAAD32nSTjepyT63rYH17n9THAAAAABED" />
          <t:Updates>
            <t:SetFolderField>
              <t:ExtendedFieldURI PropertyTag="4340"
                                  PropertyType="Boolean" />
              <t:Folder>
                <t:ExtendedProperty>
                  <t:ExtendedFieldURI PropertyTag="4340"
                                      PropertyType="Boolean" />
                  <t:Value>true</t:Value>
                </t:ExtendedProperty>
              </t:Folder>
            </t:SetFolderField>
          </t:Updates>
        </t:FolderChange>
      </m:FolderChanges>
    </m:UpdateFolder>
  </soap:Body>
</soap:Envelope>

The server responds to the UpdateFolder request with an UpdateFolderResponse message that includes a ResponseCode element value of NoError, which indicates that the folder was updated successfully, and is now hidden.

You can find all hidden folders under a parent folder by creating an extended property definition for the PidTagAttributeHidden extended property, and then using the FindFolders method to find folders with a PidTagAttributeHidden value that is set to true. This example uses the MsgFolderRoot, also known as the Top of Information Store, or IPM Subtree, as the parent folder to search under.

This example assumes that service is a valid ExchangeService object for the mailbox owner, and that the user has been authenticated to an Exchange server.

private static void FindHiddenFolders(ExchangeService service)
{
    // Create an extended property definition for the PidTagAttributeHidden property.
    ExtendedPropertyDefinition isHiddenProp = new ExtendedPropertyDefinition(0x10f4, MapiPropertyType.Boolean);

    // Create a folder view to retrieve up to 100 folders and 
    // retrieve only the PidTagAttributeHidden and the display name.
    FolderView folderView = new FolderView(100);
    folderView.PropertySet = new PropertySet(isHiddenProp, FolderSchema.DisplayName);

    // Indicate a Traversal value of Deep, so that all subfolders are retrieved.
    folderView.Traversal = FolderTraversal.Deep;

    // Find all hidden folders under the MsgFolderRoot.
    // This call results in a FindFolder call to EWS.
    FindFoldersResults findFolder = service.FindFolders(WellKnownFolderName.MsgFolderRoot,
            new SearchFilter.IsEqualTo(isHiddenProp, true), folderView);

    // Display the folder ID and display name of each hidden folder.
    foreach (Folder folder in findFolder)
    {

        Console.WriteLine("FolderId: {0}", folder.Id);
        Console.WriteLine("DisplayName: {0}", folder.DisplayName);
        Console.WriteLine("\r\n");
    }
}

You can use EWS to find all hidden folders under an existing folder by calling the FindFolder operation and searching for folders whose PidTagAttributeHidden extended property is set to true. To do this, include an IsEqualToRestriction that searches for the ExtendedFieldURI element for the PidTagAttributeHidden property (PropertyTag value to 4243 and the PropertyType value to Boolean), as shown in the following request. This example uses the MsgFolderRoot, also known as the Top of Information Store, or IPM Subtree, as the parent folder to search under.

This is also the XML request that the EWS Managed API sends when you use the FindFolders method to find all hidden folders.

<?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="Exchange2007_SP1" />
    <t:TimeZoneContext>
      <t:TimeZoneDefinition Id="Central Standard Time" />
    </t:TimeZoneContext>
  </soap:Header>
  <soap:Body>
    <m:FindFolder Traversal="Deep">
      <m:FolderShape>
        <t:BaseShape>IdOnly</t:BaseShape>
        <t:AdditionalProperties>
          <t:ExtendedFieldURI PropertyTag="4340"
                              PropertyType="Boolean" />
          <t:FieldURI FieldURI="folder:DisplayName" />
        </t:AdditionalProperties>
      </m:FolderShape>
      <m:IndexedPageFolderView MaxEntriesReturned="100"
                               Offset="0"
                               BasePoint="Beginning" />
      <m:Restriction>
        <t:IsEqualTo>
          <t:ExtendedFieldURI PropertyTag="4340"
                              PropertyType="Boolean" />
          <t:FieldURIOrConstant>
            <t:Constant Value="true" />
          </t:FieldURIOrConstant>
        </t:IsEqualTo>
      </m:Restriction>
      <m:ParentFolderIds>
        <t:DistinguishedFolderId Id="msgfolderroot" />
      </m:ParentFolderIds>
    </m:FindFolder>
  </soap:Body>
</soap:Envelope>

The server responds to the FindFolder request with a FindFolderResponse message that includes a ResponseCode element value of NoError, which indicates that the folder search was successful, as well as all the hidden folders under the root message folder.

The FolderId values are shortened for readability.

<?xml version="1.0" encoding="utf-8"?>
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header>
    <h:ServerVersionInfo MajorVersion="15"
                         MinorVersion="0"
                         MajorBuildNumber="898"
                         MinorBuildNumber="23"
                         Version="V2_10"
                         xmlns:h="http://schemas.microsoft.com/exchange/services/2006/types"
                         xmlns="http://schemas.microsoft.com/exchange/services/2006/types"
                         xmlns:xsd="http://www.w3.org/2001/XMLSchema"
                         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" />
  </s:Header>
  <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <m:FindFolderResponse xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages"
                          xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types">
      <m:ResponseMessages>
        <m:FindFolderResponseMessage ResponseClass="Success">
          <m:ResponseCode>NoError</m:ResponseCode>
          <m:RootFolder IndexedPagingOffset="6"
                        TotalItemsInView="6"
                        IncludesLastItemInRange="true">
            <t:Folders>
              <t:ContactsFolder>
                <t:FolderId Id="IBHgAAAA=="
                            ChangeKey="AwAAABYAAAD32nSTjepyT63rYH17n9THAAAAAACz" />
                <t:DisplayName>{06967759-274D-40B2-A3EB-D7F9E73727D7}</t:DisplayName>
                <t:ExtendedProperty>
                  <t:ExtendedFieldURI PropertyTag="0x10f4"
                                      PropertyType="Boolean" />
                  <t:Value>true</t:Value>
                </t:ExtendedProperty>
              </t:ContactsFolder>
              <t:ContactsFolder>
                <t:FolderId Id="IBHwAAAA=="
                            ChangeKey="AwAAABYAAAD32nSTjepyT63rYH17n9THAAAAAAC7" />
                <t:DisplayName>{A9E2BC46-B3A0-4243-B315-60D991004455}</t:DisplayName>
                <t:ExtendedProperty>
                  <t:ExtendedFieldURI PropertyTag="0x10f4"
                                      PropertyType="Boolean" />
                  <t:Value>true</t:Value>
                </t:ExtendedProperty>
              </t:ContactsFolder>
              <t:ContactsFolder>
                <t:FolderId Id="IBIQAAAA=="
                            ChangeKey="AwAAABYAAAD32nSTjepyT63rYH17n9THAAAAAADO" />
                <t:DisplayName>GAL Contacts</t:DisplayName>
                <t:ExtendedProperty>
                  <t:ExtendedFieldURI PropertyTag="0x10f4"
                                      PropertyType="Boolean" />
                  <t:Value>true</t:Value>
                </t:ExtendedProperty>
              </t:ContactsFolder>
              <t:ContactsFolder>
                <t:FolderId Id="IBHQAAAA=="
                            ChangeKey="AwAAABYAAAD32nSTjepyT63rYH17n9THAAAAAACa" />
                <t:DisplayName>Recipient Cache</t:DisplayName>
                <t:ExtendedProperty>
                  <t:ExtendedFieldURI PropertyTag="0x10f4"
                                      PropertyType="Boolean" />
                  <t:Value>true</t:Value>
                </t:ExtendedProperty>
              </t:ContactsFolder>
              <t:Folder>
                <t:FolderId Id="HAAAAA=="
                            ChangeKey="AQAAABYAAAD32nSTjepyT63rYH17n9THAAAAAACS" />
                <t:DisplayName>Conversation Action Settings</t:DisplayName>
                <t:ExtendedProperty>
                  <t:ExtendedFieldURI PropertyTag="0x10f4"
                                      PropertyType="Boolean" />
                  <t:Value>true</t:Value>
                </t:ExtendedProperty>
              </t:Folder>
              <t:Folder>
                <t:FolderId Id="IQywAAAA=="
                            ChangeKey="AQAAABYAAAD32nSTjepyT63rYH17n9THAAAeZIBf" />
                <t:DisplayName>TestFolder</t:DisplayName>
                <t:ExtendedProperty>
                  <t:ExtendedFieldURI PropertyTag="0x10f4"
                                      PropertyType="Boolean" />
                  <t:Value>true</t:Value>
                </t:ExtendedProperty>
              </t:Folder>
            </t:Folders>
          </m:RootFolder>
        </m:FindFolderResponseMessage>
      </m:ResponseMessages>
    </m:FindFolderResponse>
  </s:Body>
</s:Envelope>

After you have hidden or unhidden folders, you might want to get the folder hierarchy or synchronize the folder hierarchy. The examples that show you how to get a folder hierarchy by using the EWS Managed API or get a folder hierarchy by using EWS also indicate which folders in the hierarchy are hidden.

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