how to return a xlsx file using memorystream web api
I am successfully making a web request, creating xlsx file and saving it to a directory. I would like to stream it and return it to the client without actually saving it on the server.
this is what i am currently using, it works fine
private string generateStudyTemplate(string requestId)
{
var serviceUrl = ConfigurationManager.AppSettings["serviceUrl"];
// create webRequest
HttpWebRequest webRequest = createWebRequest(serviceUrl + "/" + requestId);
// begin async call to web request
IAsyncResult asyncResult = webRequest.BeginGetResponse(null, null);
// suspend this thread until call is complete. You might want to
// do something usefull here like update your UI
asyncResult.AsyncWaitHandle.WaitOne();
// get the response from the completed web request
var filename = string.Format("{0}.xlsx", "NewWorkbook");
string physicalPath = HttpContext.Current.Server.MapPath("/FilesForExport");
string relativePath = Path.Combine(physicalPath, filename).Replace("\\", "/");
var filePath = relativePath;
// var filePath = directory + "\\NewWorkbook.xlsx";
using (WebResponse webResponse = webRequest.EndGetResponse(asyncResult))
{
var str = webResponse.GetResponseStream();
var inBuf = new byte[webResponse.ContentLength];
var bytesToRead = Convert.ToInt32(inBuf.Length);
var bytesRead = 0;
while (bytesToRead > 0)
{
var n = str.Read(inBuf, bytesRead, bytesToRead);
if (n == 0)
break;
bytesRead += n;
bytesToRead -= n;
}
var fstr = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.Write);
fstr.Write(inBuf, 0, bytesRead);
fstr.Close();
}
return filePath;
}
private static HttpWebRequest createWebRequest(string url)
{
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
webRequest.ContentType = "text/xml;charset=\"utf-8\"";
webRequest.Accept = "text/xml";
webRequest.Method = "GET";
return webRequest;
}
Here is what I have put together from some other examples.
public HttpResponseMessage GenerateMarketStudyResult([FromBody]Result id)
{
if (id.requestId == null)
{
throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.BadRequest));
}
var serviceUrl = ConfigurationManager.AppSettings["serviceUrl"];
var streamContent = new PushStreamContent((outputStream, httpContext, transportContent) =>
{
try
{
HttpWebRequest webRequest = createWebRequest(serviceUrl + "/" + id.requestId);
IAsyncResult asyncResult = webRequest.BeginGetResponse(null, null);
asyncResult.AsyncWaitHandle.WaitOne();
using (WebResponse webResponse = webRequest.EndGetResponse(asyncResult))
{
using (MemoryStream memoryStream = new MemoryStream())
{
var str = webResponse.GetResponseStream();
var inBuf = new byte[webResponse.ContentLength];
var bytesToRead = Convert.ToInt32(inBuf.Length);
var bytesRead = 0;
while (bytesToRead > 0)
{
var n = str.Read(inBuf, bytesRead, bytesToRead);
if (n == 0)
break;
bytesRead += n;
bytesToRead -= n;
}
memoryStream.Write(inBuf, 0, bytesRead);
}
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
outputStream.Close();
}
});
streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
streamContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
streamContent.Headers.ContentDisposition.FileName = "reports.xlsx";
var result = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = streamContent
};
return result;
}
I am not getting any exceptions, but the xlsx file is returning with 0bytes.
The breakpoint here
memoryStream.Write(inBuf, 0, bytesRead);
here is the javascript serving the returned file
$http.post('/api/GenerateMarketStudyResult/', Result, { responseType: 'arraybuffer' })
.success(function (response, status, headers, config) {
saveAs(new Blob([response], { type: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" }), 'reports.xlsx');
})
shows that the
bytesRead = 112336
Answer
I assume that you write a web service which acts as a proxy between your JavaScript and some third party web service.
First of all, if you use at least .NET 4.0, you can use the Stream.CopyTo method to copy a stream to another. So instead of this:
using (WebResponse webResponse = webRequest.EndGetResponse(asyncResult))
{
var str = webResponse.GetResponseStream();
var inBuf = new byte[webResponse.ContentLength];
var bytesToRead = Convert.ToInt32(inBuf.Length);
var bytesRead = 0;
while (bytesToRead > 0)
{
var n = str.Read(inBuf, bytesRead, bytesToRead);
if (n == 0) break;
bytesRead += n;
bytesToRead -= n;
}
var fstr = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.Write);
fstr.Write(inBuf, 0, bytesRead);
fstr.Close();
}
You could write:
using (var webResponse = webRequest.EndGetResponse(asyncResult))
using (var fstr = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.Write))
{
webResponse.GetResponseStream().CopyTo(fstr);
}
Second, assuming you use WCF to build a web service, you could pipe the response to a memory stream, and return it. (dont forget to reset the stream's position after you finished writing)
Put together:
[WebGet(UriTemplate = "GenerateMarketStudyResult/{id}")]
public Stream GenerateMarketStudyResult(string id)
{
var serviceUrl = ConfigurationManager.AppSettings["serviceUrl"];
// create webRequest
HttpWebRequest webRequest = createWebRequest(serviceUrl + "/" + id);
// begin async call to web request
IAsyncResult asyncResult = webRequest.BeginGetResponse(null, null);
// suspend this thread until call is complete. You might want to
// do something usefull here like update your UI
asyncResult.AsyncWaitHandle.WaitOne();
var memStream = new MemoryStream();
// var filePath = directory + "\\NewWorkbook.xlsx";
using (WebResponse webResponse = webRequest.EndGetResponse(asyncResult))
{
webResponse.GetResponseStream().CopyTo(memStream);
}
memStream.Position = 0;
var response = WebOperationContext.Current.OutgoingResponse;
response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
response.ContentLength = (int)memStream.Length;
return memStream;
}
EDIT: You didn't copy the contents of the memoryStream to the outputStream. You can omit the memoryStream. Try this:
public HttpResponseMessage GenerateMarketStudyResult([FromBody]Result id)
{
if (id.requestId == null)
{
throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.BadRequest));
}
var serviceUrl = ConfigurationManager.AppSettings["serviceUrl"];
var streamContent = new PushStreamContent((outputStream, httpContext, transportContent) =>
{
try
{
HttpWebRequest webRequest = createWebRequest(serviceUrl + "/" + id.requestId);
IAsyncResult asyncResult = webRequest.BeginGetResponse(null, null);
asyncResult.AsyncWaitHandle.WaitOne();
using (WebResponse webResponse = webRequest.EndGetResponse(asyncResult))
{
webResponse.GetResponseStream().CopyTo(outputStream);
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
outputStream.Close();
}
});
streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
streamContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
streamContent.Headers.ContentDisposition.FileName = "reports.xlsx";
var result = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = streamContent
};
return result;
}