AD User Login protected void btnLogin_Click( object sender, EventArgs e) { string domainname = "domainname" ; try { using ( PrincipalContext pc = new PrincipalContext ( ContextType .Domain, domainname)) { // validate the credentials bool isValid = pc.ValidateCredentials(txtUserName.Text.Trim(), txtPassword.Text.Trim()); if (isValid) { UserPrincipal user = UserPrincipal .FindByIdentity(pc, txtUserName.Text.Trim()); lblstatus.Text = "Welcome " + user.Name + "," ; } else { lblstatus.Text = "Invalid Username or Password." ; } } } catch ( Exception ex) { lblstatus.Text = "Invalid Domain" ; } }