javascript - Upload files from <input type="file" multiple/> via appending to FormData -

i have form file input

<input type="file" id="fileinput" multiple /> 

and try upload files server. server-side code this:

[httppost] public actionresult index(httppostedfilebase[] files) {     ... process ... } 

for send post request use $.ajax

    var formdata = new formdata($('#formid')[     formdata.append("files", $('#fileinput')[0].files);     $.ajax({         url: "/default/index",         type: "post",         data: formdata,         contenttype: false,         processdata: false,         success: function() {             alert("success");         }     }); 

and doesn't work. if add name="files" attribute input (for native bind) , remove instruction formdata.append("files", $('#fileinput')[0].files); code works fine.

so difference between theese ways , how can pass files via appending data formdata?

note: in work can't bind form via name attribute, cause form comes template , have no name attribute.