Why are files are different when downloading from an ASP.NET (AJAX download with Blob) -


using mvc 4.0, have used following code create download files server ajax source (using latest firefox):

this works fine if output involves textual files such csv or txt files, however, when comes files zip or xlsx, seems downloaded file different original source (i.e. zip generated within server 15k, 1 downloaded 26k)

i have been struggling few days, can ask if should shred light on why works csv/text files, not zip or xlsx files?

many thanks

controller:

public function download(datain myobject) actionresult         'some processing         'generated zip files , return full path                     dim zipfullpath = generatefiles(datain)          response.clear()         response.contenttype = "application/zip"                    response.addheader("content-disposition", "attachment; filename=out.zip")         dim filelength = new io.fileinfo(zipfullpath).length         'filelength  reads 15k of data         response.addheader("content-length", filelength)         response.transmitfile(zipfullpath)         response.end()         return view()     end function

javascript:

$.ajax({     type: "post",     url: "reports/download",     data: jdata,     contenttype: "application/json; charset=utf-8",     success: function(response, status, xhr) {         // check filename         var filename = "";         var disposition = xhr.getresponseheader('content-disposition');         if (disposition && disposition.indexof('attachment') !== -1) {             var filenameregex = /filename[^;=\n]*=((['"]).*?\2|[^;\n]*)/;             var matches = filenameregex.exec(disposition);             if (matches != null && matches[1]) filename = matches[1].replace(/['"]/g, '');         }          var type = xhr.getresponseheader('content-type');         var blob = new blob([response], { type: type });          if (typeof window.navigator.mssaveblob !== 'undefined') {             // ie workaround "html7007: 1 or more blob urls revoked closing blob created. these urls no longer resolve data backing url has been freed."             window.navigator.mssaveblob(blob, filename);         } else {             var url = window.url || window.webkiturl;             var downloadurl = url.createobjecturl(blob);              if (filename) {                 // use html5 a[download] attribute specify filename                 var = document.createelement("a");                 // safari doesn't support yet                 if (typeof a.download === 'undefined') {                                     window.location = downloadurl;                 } else {                     a.href = downloadurl;                     a.download = filename;                     document.body.appendchild(a);                     a.click();                      //here problem, original 15k,                       // download file 26k                  }             } else {                                     window.location = downloadurl;             }              settimeout(function () { url.revokeobjecturl(downloadurl); }, 100); // cleanup         }     },     error: function (data) {         alert('error');     } });

currently jquery ajax can process text responses, that's why text files work binary files fail.
download non text file ajax use xmlhttprequest object , specify responsetype, instance blob or arraybuffer. 

var xhr = new xmlhttprequest(); xhr.onreadystatechange = function(){     if (this.readystate == 4 && this.status == 200){         ...         var blob = this.response; //save blob usual         ...     } } xhr.open('post', 'reports/download'); xhr.setrequestheader('content-type', 'application/json; charset=utf-8'); xhr.responsetype = 'blob'; // response blob , not text xhr.send(jdata);

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