C#TextBox设置提示文本方式(SetHintText)

[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern Int32 SendMessage(IntPtr hWnd, int msg, int wparam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);

public static void SetHintText(Control control, string text)
{
 www.chinasem.cn   SendMessage(control.Handle, 0x1501, javascript0, text);
}
public FrmUpdataPassword()
{
    InitializeComponent();
    SetHintText(txt_OldPassword, "初始密码为：123456");
    SetHintText(txt_NewPassword, $"6-{txt_NewPassword.MaxLength}位数字或字母");
    btn_Enter.Focus();
}
http://www.chinasem.cn
//显示/隐藏密码
private void chb_ShowPassword_CheckedChanged(object sender, EventArgs e)
{
    //txt_OldPassword.UseSystemPasswordChar = !chb_ShowPassword.Checked;
    txt_NewPassword.UseSywww.chinasem.cnstemPasswordChChina编程ar = !chb_ShowPassword.Checked;