How to insert Active directory users to an Active directory Group in c#

public void AddUserToADGroup(DirectoryEntry de,string _Group,string _UserName)
{
DirectorySearcher ds = new DirectorySearcher(de);
ds.Filter = "(objectClass=user)";
ds.Sort.Direction = System.DirectoryServices.SortDirection.Ascending;
ds.SearchScope = System.DirectoryServices.SearchScope.Subtree;
ds.PageSize = 4000;

string name = "";
try
{
SortedList objSortedList = new SortedList();
foreach (SearchResult result in ds.FindAll())
{
DirectoryEntry deTemp = result.GetDirectoryEntry();
name = deTemp.Name;
try
{
name = deTemp.Properties["cn"].Value.ToString();
if (name.Equals(_UserName))
{
DirectoryEntry objGrp = de.Children.Find("CN=" + _Group);

//adding new user to group
if (objGrp.Name != "")
{
objGrp.Invoke("Add", new object[] { deTemp.Path.ToString() });
objGrp.CommitChanges();
deTemp.CommitChanges();
de.CommitChanges();
}
}
}
catch (Exception ex)
{
ex.Message.ToString();
}
}
//FillGroup(ddlEmpName);
}
catch (Exception ex)
{
lblUserList.Text = ex.ToString();
}


}