Example code of IsMobile (determining device), with some handy dev functionality, see comments in code snippet.

public Boolean IsMobile
{
    get
    {
        if (HttpContext.Current == null)
            return false;

        //Making it possible to put ?showResponsive=true on any page to see it Mobile
        if (HttpContext.Current.Request.QueryString["showResponsive"] + "" == "true")
            return true;


        //Activate Mobile Channel by having an appsetting, to configure different behavior for test/dev purposes.
        //values cookie, mobiles, browsername
        if (!String.IsNullOrEmpty(ConfigurationManager.AppSettings["ResponsiveBrowser"]))
        {
            //you can have a cookie set to display the mobile channel
            HttpCookie c = HttpContext.Current.Request.Cookies.Get("ResponsiveBrowser");

            if (c == null)
                c = new HttpCookie("ResponsiveBrowser", "false");


            DeviceType deviceType = GetDevieType(HttpContext.Current.Request.UserAgent);


            if (HttpContext.Current.Request.Browser.Type.Contains(
                    ConfigurationManager.AppSettings["ResponsiveBrowser"]))
            {
                return true;
            }
            else if (ConfigurationManager.AppSettings["ResponsiveBrowser"].ToLower() == "cookie" &&
                HttpContext.Current.Request.Cookies.Get("ResponsiveBrowser") != null &&
                HttpContext.Current.Request.Cookies.Get("ResponsiveBrowser").Value == "true")
            {
                return true;
            }

            else if ((ConfigurationManager.AppSettings["ResponsiveBrowser"].ToLower() == "mobiles" &&
                deviceType == DeviceType.Phone && HttpContext.Current.Request.Cookies.Get("ResponsiveBrowser") == null) || (ConfigurationManager.AppSettings["ResponsiveBrowser"].ToLower() == "mobiles" && c.Value == "true"))
            {
                return true;
            }

            return HttpContext.Current.Request.Browser.IsMobileDevice;

        }
        return false;
    }
}

public static DeviceType GetDevieType(string userAgent)
{

    if (!String.IsNullOrEmpty(userAgent))
    {
        if (userAgent.ToLowerInvariant().Contains("blackberry")
                || userAgent.ToLowerInvariant().Contains("iphone"))
            return DeviceType.Phone;

        if (userAgent.ToLowerInvariant().Contains("ipad"))
            return DeviceType.Tablet;

        if (userAgent.ToLowerInvariant().Contains("android"))
        {
            if (userAgent.ToLowerInvariant().Contains("mobile"))
                return DeviceType.Phone;
            else
                return DeviceType.Tablet;
        }

        if (userAgent.ToLowerInvariant().Contains("windows nt") && userAgent.ToLowerInvariant().Contains("touch"))
        {
            return DeviceType.Tablet;
        }

        if (userAgent.ToLowerInvariant().Contains("windows") && userAgent.ToLowerInvariant().Contains("touch"))
        {
            return DeviceType.Phone;
        }
    }
    return DeviceType.Desktop;
}


public enum DeviceType
{
    Desktop,
    Tablet,
    Phone
}