判断客户端设备

public static bool isMobileBrowser()
{
    //GETS THE CURRENT USER CONTEXT
    HttpContext context = HttpContext.Current;

    //FIRST TRY BUILT IN ASP.NT CHECK
    if (context.Request.Browser.IsMobileDevice)
    {
        return true;
    }
    //THEN TRY CHECKING FOR THE HTTP_X_WAP_PROFILE HEADER
    if (context.Request.ServerVariables["HTTP_X_WAP_PROFILE"] != null)
    {
        return true;
    }
    //THEN TRY CHECKING THAT HTTP_ACCEPT EXISTS AND CONTAINS WAP
    if (context.Request.ServerVariables["HTTP_ACCEPT"] != null && 
        context.Request.ServerVariables["HTTP_ACCEPT"].ToLower().Contains("wap"))
    {
        return true;
    }
    //AND FINALLY CHECK THE HTTP_USER_AGENT 
    //HEADER VARIABLE FOR ANY ONE OF THE FOLLOWING
    if (context.Request.ServerVariables["HTTP_USER_AGENT"] != null)
    {
        //Create a list of all mobile types
        string[] mobiles =
            new[]
                {
                    "midp", "j2me", "avant", "docomo", 
                    "novarra", "palmos", "palmsource", 
                    "240x320", "opwv", "chtml",
                    "pda", "windows ce", "mmp/", 
                    "blackberry", "mib/", "symbian", 
                    "wireless", "nokia", "hand", "mobi",
                    "phone", "cdm", "up.b", "audio", 
                    "SIE-", "SEC-", "samsung", "HTC", 
                    "mot-", "mitsu", "sagem", "sony"
                    , "alcatel", "lg", "eric", "vx", 
                    "NEC", "philips", "mmm", "xx", 
                    "panasonic", "sharp", "wap", "sch",
                    "rover", "pocket", "benq", "java", 
                    "pt", "pg", "vox", "amoi", 
                    "bird", "compal", "kg", "voda",
                    "sany", "kdd", "dbt", "sendo", 
                    "sgh", "gradi", "jb", "dddi", 
                    "moto", "iphone"
                };

        //Loop through each item in the list created above 
        //and check if the header contains that text
        foreach (string s in mobiles)
        {
            if (context.Request.ServerVariables["HTTP_USER_AGENT"].
                                                ToLower().Contains(s.ToLower()))
            {
                return true;
            }
        }
    }

    return false;
}

来源：http://www.codeproject.com/KB/aspnet/mobiledetect.aspx