I need to find second element with the same automationid by Xpath

I need help from you. I struggling with finding by Xpath. My problem is that the software that I'm testing has one specific function where I need to scan two components (is it called two-step scan) and there are two textboxes without the name and with the same Automationid. So I need to find the second one I tried this but it does not work.

[FindsBy(How = How.Xpath, Using = "//*[@AutomationId='ScanTextBox'][1]")]
public IWebElement ScanTextBox1;

[FindsBy(How = How.Xpath, Using = "//*[@AutomationId='ScanTextBox'][2]")]
public IWebElement ScanTextBox2;

I'm using winium and I'm testing WPF application. Thanks for suggestions :)