extjs同步与异步请求互换

 onChange: function(_Field, _newValue, _oldValue) {
        if (_newValue == _oldValue) return;
        if (!_Field) return;
        if (_Field.xtype && _Field.xtype == "datefield") _newValue = _newValue.toString(); // _newValue=_newValue.format('yyyy-M-dd') ;
        this.onGetChangeValues(_Field, _newValue, _oldValue);
        _unit = {
            formid: this.form_id,
            command: '',
            key: _Field.name,
            value: _newValue
        };
        var _funid = this.id.replace(/(^Primary)/g, "");
        var url = 'Actions/WebFormSet.aspx?&Controller=EditBusiness&funcid=' + _funid;
        /**改为同步调用**/
        url += "&formid=" + this.form_id;
//        url += "&parent_formid=" + _parent_formId;
        url += "&command=";
        url += "&key=" + _Field.name;
        url += "&value=" + _newValue;
        var conn = Ext.lib.Ajax.getConnectionObject().conn;
        conn.open("GET", url, false);
        conn.send(null);
        var responseArray = conn.responseText;
        this.onChangeAjaxsuccess(conn, null);
       
       
//        Ext.Ajax.request({
//            url: url,
//            params: _unit,
//            scope: this,
//            success: this.onChangeAjaxsuccess
//        });
    },