调用前台js

this.ClientScript.RegisterStartupScript(this.GetType(), "", "<script language=\"javascript\">WindowCloseReturn();</script>");

判断当前对话框是关闭还是刷新

window.onbeforeunload = function (event) {
                var n = window.event.screenX - window.screenLeft;
                var b = n > document.documentElement.scrollWidth - 20;
                if (b && window.event.clientY < 0 || window.event.altKey) {
                    var evt = event || window.event;
                    evt.returnValue = "试卷提交将失败!确定要关闭吗？";
                }