.net directorysearcher get manager accountname
if (userAccount.Properties["manager"].Value != null)
{
DirectorySearcher search2 = new DirectorySearcher(domain.GetDirectoryEntry())
{
Filter = string.Format("(distinguishedName={0})", userAccount.Properties["manager"].Value)
};
search2.PropertiesToLoad.Add("displayName");
search2.PropertiesToLoad.Add("mail");
search2.PropertiesToLoad.Add("manager");
DirectoryEntry mgrAcc = search2.FindOne()?.GetDirectoryEntry();
}