Active Directory/LDAP :: Get The User Details Based On The Group

I am getting the details from groups but some groups have data but did not return any data is there any problem with this code. some groups have returned data.

CN=Tets App_Reviewer,OU=Tets Appl Groups,OU=District Wide Groups,DC=tets,DC=com;

Tets App_Reviewer is the group name

public List<ADUserDetail> GetUserFromGroup(String groupName)
{
List<ADUserDetail> userlist = new List<ADUserDetail>();
try
{
_directoryEntry = null;
DirectorySearcher directorySearch = new DirectorySearcher(SearchRoot);
directorySearch.Filter = "(&(objectClass=group)(SAMAccountName=" + groupName + "))";
SearchResult results = directorySearch.FindOne();
if (results != null)
{
DirectoryEntry deGroup = new DirectoryEntry(results.Path, LDAPUser, LDAPPassword);
System.DirectoryServices.PropertyCollection pColl = deGroup.Properties;
int count = pColl["member"].Count;
for (int i = 0; i < count; i++)
{
string respath = results.Path;
string[] pathnavigate = respath.Split("CN".ToCharArray());
respath = pathnavigate[0];
string objpath = pColl["member"][i].ToString();
string path = respath + objpath;
DirectoryEntry user = new DirectoryEntry(path, LDAPUser, LDAPPassword);
ADUserDetail userobj = ADUserDetail.GetUser(user);
userlist.Add(userobj);
user.Close();
}
}
return userlist;
}
catch (Exception ex)
{
return userlist;
}
}