Geocode function returns 500 code and codestatus Servererror

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C#

ASP.NET

I am using googlemaps.subgurim.net google map in my project. Geocode funtion was some times not working in server system,here i am converting latitude and longitude to human readable address.some times geocode staus returns 500 and server error,this time this code not working.when
geocode returns 500 code and server error that time lat,lng address was not coming...

string sMapKey = ConfigurationManager.AppSettings["googlemaps.subgurim.net"];
                    GeoCode objAddress = new GeoCode();
                    objAddress = GMap.geoCodeRequest(new GLatLng(Convert.ToDouble(status.Rows[0][0]), Convert.ToDouble(status.Rows[0][1])), sMapKey);
StringBuilder sb = new StringBuilder();
                    if (objAddress.valid)
                    {
                        sb.Append(objAddress.Placemark.address.ToString());
                        string address = sb.ToString();
                        lblPlace.Text = address;
                    }