In Asp.NET , when we want to create a modal dialog box we can use the javascript like

vReturnValue = window.showModalDialog(sURL [, vArguments] [, sFeatures])Detail in MSDN. But there is a problem,if we have to post to server in modal dialog box , you can findanother window will be opened and an error box will be shown.To resolve it we can use FRAMESET , that's to say we create a aspx file include FRAMESETin which link to the page we want to show in modal dialog box.