Login Autherntication using LDAP in asp.net

protected void btnSubmit_Click(object sender, ImageClickEventArgs e)
    {
        try
        {
            string path = ConfigurationSettings.AppSettings["ldap"].ToString();
            DirectoryEntry objEntry = new DirectoryEntry(path, txtUserName.Text.Trim(), txtPassword.Text.Trim());
            DirectorySearcher search = new DirectorySearcher(objEntry);
            search.Filter = "(&(objectCategory=person)(SAMAccountName=" + txtUserName.Text.Trim() + "))";
            //search.Filter = "(&(objectCategory=person)(SAMAccountName=AjayK))";
            SearchResult result = search.FindOne();
            if (result != null)
            {
                DirectoryEntry de = result.GetDirectoryEntry();
                PropertyValueCollection groups = de.Properties["memberOf"];

                foreach (string s in groups)
                {
                    //Response.Write(s + "<br/>");
                    if (s.Contains("Managers ABC"))
                        Session["isMgr"] = true;
                }
                Session["name"] = txtUserName.Text.Trim();
                //Session["name"] = "rupeshm";
                Response.Redirect("Index.aspx");
            }
        }
        catch (DirectoryServicesCOMException)
        {
            {
               
              lblMsg.Text = "Invalid User Name or Password!!";
           
            }
        }
    }