//循环遍历 <tbody id="linedata2">,获取每行值对比

$("#linedata2 tr").each(function(i,n){

    var mappingProjectCode = $("mappingProjectCode",this).val();

    if(mappingProjectCode == null || mappingProjectCode == ''){

        must+="第("+(i+1)+")行xxx不能为空! ";

        errorFlag=true;

    }

});