AdvancedWebDriverUsageTests.cs

public void WaitForAjaxComplete(int maxSeconds)
{
    bool isAjaxCallComplete = false;
    for (int i = 1; i <= maxSeconds; i++)
    {
        isAjaxCallComplete = (bool)((IJavaScriptExecutor)driver).
        ExecuteScript("return window.jQuery != undefined && jQuery.active == 0");

        if (isAjaxCallComplete)
        {
            return;
        }
        Thread.Sleep(1000);
    }
    throw new Exception(string.Format("Timed out after {0} seconds", maxSeconds));
}