谁帮我看看这段combox 从数据库取值显示的问题？？

    var store_sdz = new Ext.data.JsonStore({
        url:'Data/dangan/GetCompany.aspx',
        fields:['companyid','companyname']
    });
    
    store_sdz.load();
   
    var combo_sdz = new Ext.form.ComboBox({
        store:store_sdz,
        id:'com_thfs',
        fieldLabel:'送达站',
        hiddenName:'thfs',
        width:85,
        emptyText:'请选择...',
        mode:'local',
        triggerAction:'query',
        valueField:'text',
        displayField:'text',
        selectOnFocus:true,
        allowBlank:false,
        blankText:'请选择送达站'
    });  
怎么不显示？