How to get Users form Active directory

public static DataSet GetUsersForGroup(string GroupName) {
DataSet dsUser = new DataSet(); DirectoryEntry de = GetDirectoryObject();
//create instance fo the direcory searcher DirectorySearcher deSearch = new DirectorySearcher();
//set the search filter deSearch.SearchRoot =de;
//deSearch.PropertiesToLoad.Add("cn");
deSearch.Filter = "(&(objectClass=group)(cn=" + GroupName +"))";
//get the group result SearchResult results= deSearch.FindOne();
//Create a new table object within the dataset DataTable tbUser = dsUser.Tables.Add("Users"); tbUser.Columns.Add("UserName");
tbUser.Columns.Add("DisplayName");
tbUser.Columns.Add("EMailAddress");
//Create default row DataRow rwDefaultUser = tbUser.NewRow();
rwDefaultUser ["UserName"]= "0"; rwDefaultUser ["DisplayName"]="(Not Specified)"; rwDefaultUser ["EMailAddress"]="(Not Specified)";
tbUser.Rows.Add(rwDefaultUser);
//if the group is valid, then continue, otherwise return a blank dataset if(results !=null) { //create a link to the group object, so we can get the list of members
//within the group DirectoryEntry deGroup= new DirectoryEntry(results.Path,ADAdminUser,ADAdminPassword,AuthenticationTypes.Secure);
//assign a property collection System.DirectoryServices.PropertyCollection pcoll = deGroup.Properties; int n = pcoll["member"].Count;
//if there are members fo the group, then get the details and assign to the table for (int l = 0; l < n ; l++)
{
//create a link to the user object sot hat the FirstName, LastName and SUername can be gotten DirectoryEntry deUser= new DirectoryEntry(ADFullPath + "/" +pcoll["member"][l].ToString(),ADAdminUser,ADAdminPassword,AuthenticationTypes.Secure);
//set a new empty row DataRow rwUser = tbUser.NewRow();
//populate the column rwUser["UserName"]= GetProperty(deUser,"cn"); rwUser["DisplayName"]= GetProperty(deUser,"givenName") + " " + GetProperty(deUser,"sn"); rwUser["EMailAddress"]= GetProperty(deUser,"mail");
//append the row to the table of the dataset tbUser.Rows.Add(rwUser);
//close the directory entry object deUser.Close();
}
de.Close();
deGroup.Close();
}