Open an .aspx page with the window.showModalDialog

I open my aspx search page using the window.showModalDialog. When I then click on an
<asp:Button> to actually do the search to retrieve data for my datagrid, It opens up another instance of the same search window. If I open the initial seach window with a window.open
then when I click on search the datagrid is populated in the opened window.Put <base target="_self">
in header section of you dialog
Thanks for your help.
That was it.