c# - base.EndInvoke throws timeoutException when table is 1MB -

i have silverlight application adds 120 rows sql table once hour. done wcf service (using linq sql). after 12 hours of running program, throws exception in references.cs (which created automatically). exception message:

the http request 'http://localhost:64739/sqlservice.svc' has exceeded allotted timeout. time allotted operation may have been portion of longer timeout. 

if stop application , rerun here add 13th hour data , throws exception on 14th. problem might related sql table size, since throws first timeout exception when table size becomes 1mb. ideas?

this exception catched:

public void endaddtables(system.iasyncresult result) {                  object[] _args = new object[0];                 base.endinvoke("addtables", _args, result);   } 

and addtables code:

    [operationcontract]     public void addtables(short id, string temperature, string humidity,                 string wind, ...)     {         weatherdataclassdatacontext db = new weatherdataclassdatacontext();         weather_info row = new weather_info();           row.officeid = id;         row.temperature = temperature;         row.humidity = humidity;          db.weather_infos.insertonsubmit(row);         db.submitchanges();         db.refresh(system.data.linq.refreshmode.keepcurrentvalues, db.weather_infos);     }