How to handle the WebService Exceptions?

Include System.Net reference and follow the code below

public static bool CheckForInternetConnection()
{
    try
    {
        using (var client = new WebClient())
        using (var stream = client.OpenRead("http:\\www.google.com"))
        {
            return true;//Tried pinging the site that almost up all the time.
        }
    }
    catch
    {
        return false;
    }
}

Call the above function where you want to check connection availability and throw the error like

Response.Write("<script type='text/javascript'>");
Response.Write("alert('Check Internet Connection.');");
Response.Write("</script>");

By this you can check weather internet is available or not.Further,refer to below links

check internet connection available or not in c# [^]

How to Ping network IP or Hostname in Silverlight Application?[^](Its based on silverlight but will help you bit)