function doSelectOk() {
        var objSelected = document.getElementById("lbUserSelected");
        var selectItemCount = objSelected.options.length;
        var objhfSelectIDList = document.getElementById("hfSelectIDList");
        var returnValue = "";
        var returnText = "";
        for (var i = 0; i < selectItemCount; i++) {
            var optionValue = objSelected.options[i].value;
            var optionText = objSelected.options[i].text;
            if (!IsNull(returnValue)) {
                returnValue += ",";
                returnText += ",";
            }
            returnValue += optionValue;
            returnText += optionText;
        }
        var param = new modalDialogParams();
        param.ValueParam = returnValue;
        param.TextParam = returnText;

        var objResult = param;
        objhfSelectIDList.valve = param.ValueParam;
        alert(objhfSelectIDList.valve);
        window.returnValue = objResult;
        window.close();
    }

页面：通过<asp:HiddenField runat="server" />传值在后台里 string IDList = hfSelectIDList.Value.Trim(); 不知道为啥IDList 老是为空！请大家帮忙解决一下哈 谢谢！！！