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How to: Obtain Members of an Exchange Distribution List

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This example lets the user select an Exchange distribution list from the Select Names dialog box and expands the distribution list to display its members.

This code sample calls the GetExchangeDistributionListMembers method of the ExchangeDistributionList object to get an AddressEntries collection that contains all the members of the list. Because distribution lists can be nested inside another distribution list, the returned AddressEntries collection can represent any type of Exchange AddressEntry object.


Expanding distribution lists can create a performance burden on an Exchange server, so use the GetExchangeDistributionListMembers method cautiously. Expect that your code will be slow when it expands large distribution lists.

To obtain the members of a distribution list, the user must be connected to an Exchange server and online.

If you use Microsoft Visual Studio to test this code sample, you must first add a reference to the Microsoft Outlook 12.0 Object Library component and specify the Outlook variable when you import the Microsoft.Office.Interop.Outlook namespace. The Imports or using statements must not occur right before the functions in the Code section but must be added before the public Class declaration. The following lines of code show how to do the import and assignment in Visual Basic and in C#:

using Outlook = Microsoft.Office.Interop.Outlook;
private void GetDistributionListMembers()
    Outlook.SelectNamesDialog snd =
    Outlook.AddressLists addrLists =
    foreach (Outlook.AddressList addrList in addrLists)
        if (addrList.Name == "All Groups")
            snd.InitialAddressList = addrList;
    snd.NumberOfRecipientSelectors =
    snd.ToLabel = "D/L";
    snd.ShowOnlyInitialAddressList = true;
    snd.AllowMultipleSelection = false;
    if (snd.Recipients.Count > 0)
        Outlook.AddressEntry addrEntry =
        if (addrEntry.AddressEntryUserType ==
            Outlook.ExchangeDistributionList exchDL =
            Outlook.AddressEntries addrEntries =
            if (addrEntries != null)
                foreach (Outlook.AddressEntry exchDLMember
                    in addrEntries)