newTab.cs

// This sample assumes driver is a valid IWebDriver, and that
// elementThatPopsUpNewTab is a valid, already located IWebElement
// that, when clicked, follows a link that will open a new tab.
IList<string> existingHandles = driver.WindowHandles;
elementThatPopsUpNewTab.Click();
WebDriverWait wait = new WebDriverWait(driver, TimeSpan.FromSeconds(5));
string newTabHandle = wait.Until<string>((d) =>
{
    string foundHandle = null;
    IList<string> differentHandles = d.WindowHandles.Except(existingHandles).ToList();
    if (differentHandles.Count > 0)
    {
        foundHandle = differentHandles[0];
    }

    return foundHandle;
});
driver.SwitchTo().Window(newTabHandle);

This code give me error: "Timed out after 5 seconds"

@MESWEB Then you'll need to provide some code of your own that uses a real site that is failing for you.