How to select Iframe in Selenium?

I want select Iframe with id="iframe00237" and data inside it:

This is HTML:

<iframe src="http://example/iframe/v2.html?id=5225dddd-588a-49c2-961e-e3417cf5a728  scrolling="no" frameborder="0" marginwidth="0" marginheight="0" width="100%" height="100%" allowfullscreen="true" webkitallowfullscreen="true" mozallowfullscreen="true" id="iframe09328" class="sm_iframe"></iframe>
    <body>
        <div>
            <iframe src="http://example.com/main?id=aab0619b-a938-4f00-b545-742fff5e1118&amp;crtdt=1461214262&amp; scrolling="no" frameborder="0" marginwidth="0" marginheight="0" allowfullscreen="allowfullscreen" id="iframe05443" class="sm_iframe" style="left: 0px; top: 0px; width: 730px; height: 411px;"></iframe>
        </div>
        <div>
            <iframe src="http://example.com/main?id=5225dddd-588a-49c2-961e-e3417cf5a728&amp scrolling="no" frameborder="0" marginwidth="0" marginheight="0" allowfullscreen="allowfullscreen" id="iframe00237" class="sm_iframe" style="left: 0px; top: 0px; width: 811px; height: 456px;"></iframe>
        </div>
    </body>

Iframe src="url" url is random..

I'm finding in Stackoverflow and try with code:

//Select parent frame
IWebElement parentFrame = driver.FindElement(By.XPath("//iframe[@id='iframe09328']"));
driver.SwitchTo().Frame(detailFrame);

//Current we on detailFrame continues to go to childFrame.
IWebElement childFrame = driver.FindElement(By.XPath("//iframe[@id='iframe00237']"));
driver.SwitchTo().Frame(childFrame);

In debug mode, parentFrame and childFrame always null values.

How to resolve my problem? I also try FindElement by ID.

In case the ID is static, you can use By.Id(). See code below:

IWait<IWebDriver> wait = new DefaultWait<IWebDriver>(driver);
wait.Timeout = TimeSpan.FromSeconds(10);
wait.PollingInterval = TimeSpan.FromMilliseconds(300);
By by = By.Id("iframe09328");
try
{
    // Switch to the parent iframe
    wait.Until(d => d.FindElements(by).Count > 0);        
    IWebElement parentFrame = driver.FindElements(by).First();
    driver.SwitchTo().Frame(parentFrame);

    // Switch to the inner iframe
    by = By.Id("iframe00237");
    wait.Until(d => d.FindElements(by).Count > 0);
    IWebElement childFrame = driver.FindElements(by).First();
    driver.SwitchTo().Frame(childFrame);
}
catch (Exception)
{
    throw new NoSuchElementException("Unable to find element, locator: \"" + by.ToString() + "\".");
}

If this doesn't work, please give us the exception "Unable to find element, locator: ......"