thanks for reply but i try that and result is null or no data on the onupdate()
i will illustrate my case it may differ and give you example of what happened.
my adapter sends the updates to the lightstreamer only one time at 3.30 pm then the client open the application at 4.00 pm and subscribe for the items.
if the client opened the app at 3.30 or befor, the data returned.
but in my case and when i use true and false cases, data returned null or no data.
i need if the adapter sends the data only one time to the lightstreamer and then in any after time the client opens the app and subscribe, he can get data correctly.