C# ขอ คำสั่ง ASP.NET เชื่อมผ่าน AD (Active Directory)

    void Page_Load(object sender, EventArgs e) {
    }
    
    protected void btnLogin_Click(object sender, System.EventArgs e) {
        string DomainAndUsername = "";
        string strCommu;
        bool flgLogin = false;
        strCommu = ("LDAP://" 
                    + (initLDAPServer + ("/" + initLDAPPath)));
        DomainAndUsername = (initShortDomainName + ("\\" + txtUser.Text));
        DirectoryEntry entry = new DirectoryEntry(strCommu, DomainAndUsername, txtPwd.Text);
        object obj;
        try {
            obj = entry.NativeObject;
            DirectorySearcher search = new DirectorySearcher(entry);
            SearchResult result;
            search.Filter = ("(SAMAccountName=" 
                        + (txtUser.Text + ")"));
            search.PropertiesToLoad.Add("cn");
            result = search.FindOne();
            if ((result == null)) {
                flgLogin = false;
                strErrMsg = "Please check user/password";
            }
            else {
                flgLogin = true;
            }
        }
        catch (Exception ex) {
            flgLogin = false;
            strErrMsg = "Please check user/password";
        }
        if ((flgLogin == true)) {
            this.lbDisplay.Text = ("Welcome " + txtUser.Text);
        }
        else {
            this.lbDisplay.Text = strErrMsg;
        }
    }