To refresh the parent page after the showModalDialog is closed follow the below code.

On Parent page button click event write the below code to open the showModalDialog popup.

function OpenmodalDailg() {

            window.showModalDialog("childPage.aspx", 'ChildPage', 'scroll:no;resizable:no;dialogWidth:633px;dialogHeight:437px');

            __doPostBack('', '');



        }



On popup window write the below code to execute while the close button is clicked.



function ClosebtnClick() {

window.close()

}