easyui表单提交无效

Question

1.使用a标签的点击事件提交，代码如下
jsp:

<form id="modifyForm" method="post" enctype="multipart/form-data">
            <p>&nbsp;&nbsp;&nbsp;ID：<input id="fid" name="fid" readonly="readonly"/></p>
            <p><input id="fpic" type="file" name="picData" onchange="chgPic(this)"/><br>
                <img src="rel/images/not_pic.jpg" id="pic" width="100" height="100">
            </p>
            <p><a class="closeBtn" href="javascript:void(0)">关闭</a>&nbsp;&nbsp;
            <a class="updateBtn"  href="javascript:void(0)">修改</a></p>
        </form>

js

$(".updateBtn").linkbutton({
    iconCls: "icon-ok",
    onClick: function(){
        //alert(0);
        $("#modifyForm").form('submit',{
            url:"flowers/uploadpic",    
            success:function(data){ 
                alert(1);
                if(data == ""){
                    $.messager.alert('图片上传','图片上传失败 ！','warning');
                    $("#modifyDiv").dialog("close"); //关闭修改框
                    return ;
                }
                if(data.trim() == "true"){
                    $("#modifyDiv").dialog("close"); //关闭修改框
                    $("#flowerInfo").datagrid("reload"); //刷新修改数据
                }else{
                    $.messager.show({
                        title:'修改信息',
                        msg:'修改失败！！！',
                        showType:'show',
                        style:{
                            top:document.body.scrollTop+document.documentElement.scrollTop,
                        }
                    });
                }
            } 
        });
        //$("#modifyForm").submit();
    }     
});