form表单使用ajaxsubmit上传文件，并验证

<form id="pro_change">
<label>商品名称：</label><input type=text name="proname"id="uptdogPro_name" class="myinput">
<input type="hidden" name="proid" id="upproid" value="${loginUser.vuid}"/>
<label style="padding-left:100px;">商品规格：</label><input type=text name="nature"id="uptdogPro_nature" class="myinput"><br /> <br />
<label>品牌名称：</label><select name="brandid" id="uptdogPro_brname"class="myinput"  style="width:145px;"></select>
<label style="padding-left:100px;">商品图片：</label><input type=file name="pictrues" id="uptdogPro_pic" multiple="multiple" onchange="previewMultipleImage(this,'uptpro_pic_show')"><br /> <br />
<label>所属类型：</label><select name="fid" id="uptdogPro_finame"class="myinput" style="widt
4000
h:145px;" onChange="changeER()"></select>
<label style="padding-left:100px;">所属分类：</label><select name="tid" id="uptdogPro_tpname"class="myinput"></select><br /> <br />
<label>市 场 价 ： </label><input type=text name="promarprice"id="uptdogPro_marpri" class="myinput">
<label style="padding-left:100px;">波 奇 价 ： </label><input type=text name="bqpri"id="uptdogPro_bqpri" class="myinput"><br /> <br />
<label>商品销量：</label><input type=text name="prosales"id="uptdogPro_sales" class="myinput">
<label style="padding-left:100px;">商品库存：</label><input type=text name="inventory" id="uptdogPro_inven" class="myinput"><br /> <br />
<label>商品状态：</label><select name="status" id="uptdogPro_status"class="myinput"></select><br /> <br />
<label style="float:left;">商品介绍：</label><input type=file name="prointros" id="uptdogPro_intro" onchange="previewMultipleImage(this,'upproinfo_pic_show')"><br /> <br />
<a href="javascript:uptDogProInfo()" class="easyui-linkbutton" data-options="iconCls:'icon-edit'">修改</a>
</form>

function uptDogProInfo(){
var ajax_option={
url:"productinfo_changeproducttt.action",//form 的action
type:"post",  //form 的method方法
beforeSubmit:checkUppro,  //在表达提交前执行的验证函数
contentType: "application/x-www-form-urlencoded; charset=utf-8",   //设置编码集
success:function(data){  //表单提交成功后执行的函数
alert("执行成功！");
}
}
$('#pro_change').ajaxSubmit(ajax_option);
}