/// <summary>
/// Gets the list of audience names and GUIDs for the current site
/// </summary>
/// <returns>
/// A SortedList object where the keys are the audience names (string)
/// and the values are the audience GUIDs (System.Guid)
/// </returns>
public SortedList GetAudienceAndGuidList()
{
    var audList = new SortedList();
    var assemblyInstance = Assembly.LoadWithPartialName("Microsoft.SharePoint.Portal");
    if (assemblyInstance != null)
    {
        // We're working on a SharePoint Portal Server, or a WSS site on a server with SPS
        // Get the current portal context
        var portalContext = assemblyInstance.GetType("Microsoft.SharePoint.Portal.PortalContext");
        var currentContextProperty = portalContext.GetProperty("Current");
        var currentContext = currentContextProperty.GetValue(null, null);
        if (currentContext != null)
        {
            // We have a portal context, so we're on SPS
            // Get the types we'll be working with
            var audMgrType = assemblyInstance.GetType("Microsoft.SharePoint.Portal.Audience.AudienceManager");
            var audCollType = assemblyInstance.GetType("Microsoft.SharePoint.Portal.Audience.AudienceCollection");
            var audType = assemblyInstance.GetType("Microsoft.SharePoint.Portal.Audience.Audience");
            // Create the AudienceManager object
            var audMgr = audMgrType.InvokeMember(null,
                BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.CreateInstance, null, null, new object[] { currentContext });
            // Call the Audiences property to get the collection of audiences from the AudienceManager
            var audColl = (IEnumerable)audMgrType.InvokeMember("Audiences", BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetProperty, null, audMgr, null);
            // Get the name and GUID for each audience and put them in the collection
            foreach (var aud in audColl)
            {
                try { var audName = (string)audType.InvokeMember("AudienceName", BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetProperty, null, aud, null); var audGuid = (Guid)audType.InvokeMember("AudienceID", BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetProperty, null, aud, null); audList.Add(audName, audGuid); }
                catch (Exception exc)
                {
                    // If there are any problems, don't add the audience to the list
                    System.Diagnostics.Debug.WriteLine("EXCEPTION getting audience and guid list: " + exc.Message);
                }
            }
        }
    }
    return audList;
}

/// <summary>
/// Uses System.Reflection to late-bind to the Microsoft.SharePoint.Portal assembly and determine if
/// a user is a member of an audience.
/// </summary>
/// <param name="username">The username of the person to look up</param>
/// <param name="audienceID">The audience ID to check membership for</param>
/// <returns>True if the user is a member of the specified audience; false otherwise</returns>
public bool UserIsMemberOfAudience(string username, Guid audienceID)
{
    var assemblyInstance = Assembly.LoadWithPartialName("Microsoft.SharePoint.Portal"); if (assemblyInstance != null)
    {
        // We're working on a SharePoint Portal Server, or a WSS site on a server with SPS
        // Get the current portal context
        var portalContext = assemblyInstance.GetType("Microsoft.SharePoint.Portal.PortalContext"); var currentContextProperty = portalContext.GetProperty("Current"); var currentContext = currentContextProperty.GetValue(null, null); if (currentContext != null)
        {
            // We have a portal context, so we're on SPS
            // Get the types we'll be working with
            var audMgrType = assemblyInstance.GetType("Microsoft.SharePoint.Portal.Audience.AudienceManager");
            // Create the AudienceManager object
            var audMgr = audMgrType.InvokeMember(null, BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.CreateInstance, null, null, new object[] { currentContext });
            // Call the IsMemberOfAudience method to determine audience membership
            var userIsMember = false; var isMemberOfAudienceArgs = new object[] { username, audienceID }; try { userIsMember = (bool)audMgrType.InvokeMember("IsMemberOfAudience", BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.InvokeMethod, null, audMgr, isMemberOfAudienceArgs); }
            catch (Exception err)
            {
                // Do nothing
                System.Diagnostics.Debug.WriteLine("EXCEPTION determining audience membership:\n" + err.Message);
            }
            return userIsMember;
        }
        else
        {
            // We're working in WSS, which doesn't have audiences, so we'll assume that everyone
            // is a member of every audience.
            return true;
        }
    }
    else
    {
        // We're working in WSS, which doesn't have audiences, so we'll assume that everyone
        // is a member of every audience.
        return true;
    }
}