List<TagInfo> securityTags = new List<TagInfo>();
AssignedTagCollection tagCollection = null;

TrusteeInfo trustee = Trustee.GetInfo(new AccountReference(userName, LFSession), LFSession);
tagCollection = trustee.Tags;

foreach (AssignedTag tag in tagCollection)
{
       if (tag.IsSecure == true) securityTags.Add((TagInfo)tag);
}

return securityTags;

The assigned tags can not be converted to TagInfo. So I get the same error if I do: 'foreach (TagInfo tag in tagCollection)'. This probably has an easy solution, but my brain isn't working today. I know I could just return a list of id's or strings, but I would rather return a list of TagInfo.