Add rows to a Table in run time , one by one

 Hi,
I would like to add rows to a table at run time by clicking a button. Every time I click the button I need one row to be added to the table. what I did now is by clicking the button on row is created and is filled with the table cells but the problem is each time I can add only one row to the table, when I click to add another the old row will be replaced with the new one , therefore I have one row in the table everytime.
please advise.
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