Pass values from chid window to parent window

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ASP.NET

In my form i have dropdown list and a "New" Button.when i click "new" button a child window will open.In child window a textbox and "Save" button.When i click save button .Add new value in sql ,refresh parent window and close the child window.
My question is how to set dropdown selected value to newly added value from child window.after closing child window.
I use following code to refresh and close child window

Response.Write("<script language='javascript'> { opener.document.location.reload(true)  }</script>");
         
            Response.Write("<script language='javascript'> { self.close() }</script>");