Hide ModalPopupExtender from code behind

I am working on asp.net , c sharp code
In my code when any particular condition is true, I need to fetch data from database and need to show in popup.
I have created ModalPopupExtender which contains datagrid and some labels
I bring the data in dataset and bind this data to datagrid.
But whenever page load occurs this popup blinks with blank data.
How to hide this ModalPopupExtender on pageload from code behind.
I have tried with ModalPopupExtender.Hide(), but it did not worked
Please help...