using "hashtable" and getting values in .cs file

hashtable at "dao"
public Hashtable GetEmpGroups(string emploginId)
{
Hashtable hashEmpGroups = new Hashtable();
SqlConnection conn = new SqlConnection(_connStr);
StringBuilder gname = new StringBuilder();
StringBuilder id = new StringBuilder();
string sqlQury = "SELECT LG.GROUP_NAME,LEG.GROUP_ID FROM LMS_EMP_GROUP LEG LEFT JOIN LMS_GROUP LG ON LEG.GROUP_ID=LG.GROUP_ID WHERE EMP_LOGIN_ID='" + emploginId + "'";
try
{
conn.Open();
SqlDataReader dr = SqlHelper.ExecuteReader(_connStr, CommandType.Text, sqlQury);
while (dr.Read())
{
if (gname.ToString() == "")
{
gname.Append(dr[0].ToString());
id.Append(dr[1].ToString());
}
else
{
gname.Append("," + dr[0].ToString());
id.Append("," + dr[1].ToString());
}
}
hashEmpGroups.Add("Groups", gname);
hashEmpGroups.Add("GroupIds", id);
dr.Close();
dr.Dispose();
return hashEmpGroups;
}
catch (Exception ex)
{
throw new ApplicationException(ex.Message);
}
finally
{
conn.Close();
conn.Dispose();
}
}

getting hashtable values at .cs file
Hashtable groupnames=GetEmpGroups(emp.EmpLoginId);
dr[3] = groupnames["Groups"].ToString();