Develop Reference

Trouble making POST request from c# [.NET]

We have a created an API for the application which takes the image via POST request process it and sends the result in JSON format.
We tried calling API from different sources like python, postman app, c#. We can successfully call end point using python and postman app but with c# getting error
c# code [Not working]
byte[] img_data = System.IO.File.ReadAllBytes(#"file_path");
string url_ep = "http://ip:port/get";
Dictionary<string, byte[]> fl_image = new Dictionary<string, byte[]>();
fl_image.Add("image", img_data);
string data = JsonConvert.SerializeObject(fl_image);
var dataToSend = Encoding.UTF8.GetBytes(data);
var request = HttpWebRequest.Create(url_ep);
request.ContentType = "application/json";
request.ContentLength = dataToSend.Length;
request.Method = "POST";
request.GetRequestStream().Write(dataToSend, 0, dataToSend.Length);
var response = request.GetResponse();
System.IO.Stream dataStream = response.GetResponseStream();
System.IO.StreamReader reader = new System.IO.StreamReader(dataStream);
// Read the content.
string responseFromServer = reader.ReadToEnd();
Console.WriteLine(responseFromServer);
python code [working]
import requests
url = 'http://ip:port/get'
fl_image = {'image': open('file_path', 'rb')}
res = requests.post(url, files=fl_image)
print(res.json())
API Endpoint
from flask import Flask, request
import numpy as np
import cv2 as cv
#app.route('/get', methods = ['POST'])
def get_image():
if request.method == 'POST':
file = request.files['image']
# Read file
f = file.read()
# convert string of image data to uint8
f1 = np.fromstring(f, np.uint8)
# decode image
f2 = cv.imdecode(f1,cv.IMREAD_COLOR)

There are several issues with the way you are posting data from C#. The most relevant one is that you are trying to post a file as a JSON object, with file contents as string.
This cannot work: your python server is clearly expecting multipart/form-data as content-type.
I also strongly recommend you to use HttpClient and not the old HttpWebRequest class to send HTTP Requests.
var filePath = #"file_path";
var url = "http://ip:port/get";
using (var client = new HttpClient())
using (var content = new MultipartFormDataContent())
using (var fileStream = File.OpenRead(filePath))
{
var imageContent = new StreamContent(fileStream);
// NOTE: the line below is not required, but useful when you know the media type
imageContent.Headers.ContentType = MediaTypeHeaderValue.Parse("image/jpeg");
content.Add(imageContent, "image", Path.GetFileName(filePath));
var response = await client.PostAsync(url, content);
var stringResponse = await response.Content.ReadAsStringAsync();
// do what you need with the response
}
Other minor issues:
Do not read the entire file in memory (using File.ReadAllBytes), but open a stream for reading instead.
Use async/await when possible, do not block on async code (do not use .Result, .Wait() or .GetAwaiter().GetResult() on Task or Task<T>)
Always call Dispose() on IDisposable objects when you have finished using them (wrapping them inside a using block)

You need to dispose the connections
reader.Close();
dataStream.Close();
response.Close();
Hope this helps
Or try using HttpClient for .net within the using block

How to Post a web request and receive a file from web API response?

I have an Infopath Form Template on Sharepoint, I want to add a button there so when the user clicks on it, it will POST an string to the following Web API. The following web API is tested and returns an excel file as shown:
I want to Post the FileName of the excel file using post request and it is important for me the request method to be POST type. and then the user will download a file with the specified 'FileName'.
Actually i want to use post method because at the next stage i will send the content of the excel file too.
Important Note: I only can use .Net FrameWork 3.5 because this is the only framework supported in InfoPath Form Templates.
[HttpPost]
public HttpResponseMessage Post([FromBody]string FileName)
{
string reqBook = "c:\somefile.xlsx";
//converting Excel(xlsx) file into bytes array
var dataBytes = File.ReadAllBytes(reqBook);
//adding bytes to memory stream
var dataStream = new MemoryStream(dataBytes);
HttpResponseMessage httpResponseMessage = Request.CreateResponse(HttpStatusCode.OK);
httpResponseMessage.Content = new StreamContent(dataStream);
httpResponseMessage.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
httpResponseMessage.Content.Headers.ContentDisposition.FileName = FileName;
httpResponseMessage.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/octet-stream");
return httpResponseMessage;
}

When you perform the HttpPost on the client side, you will want to read the HttpResponseStream to get the byte data of the response stream.
Once you have the response stream data, you can then deserialize it to the type of object in C# you want, or you could alternatively just write it to the disk as
File.WriteAllBytes("someexcel.xlsx",data);
An easy way to do it would be with the HttpClient class.
HttpClient client = new HttpClient();
var response = client.PostAsync("", null).Result;
var content = response.Content.ReadAsByteArrayAsync().Result;
File.WriteAllBytes("excel.xlsx", content);
Just fill in the PostAsync bit with the Url and the content you wish to post.
I am using .Result to keep everything synchronous - but you can use 'await' if you prefer.
If you are working with HttpWebRequests - then the process becomes more complicated, as you need to manage the streams yourself.
The HttpClient will manage and handle it all for you - so I recommend it, unless there is something special it needs to do that it currently does not.
Due to your .Net 3.5 requirement:
private static HttpWebResponse MakeRequest(string url, string postArgument)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "POST";
request.ContentType = "multipart/form-data;";
Stream stream = request.GetRequestStream();
string result = string.Format("arg1={0}", postArgument);
byte[] value = Encoding.UTF8.GetBytes(result);
stream.Write(value, 0, value.Length);
stream.Close();
return (HttpWebResponse)request.GetResponse();
}
You can then do:
var response = MakeRequest("http://mywebsite.com/ProcessExcel", "accounts.xlsx");
And then do
Stream objStream = response .GetResponseStream();
BinaryReader breader = new BinaryReader(objStream);
byte[] data= breader.ReadBytes((int)webresponse.ContentLength);
File.WriteAllBytes("excel.xlsx",data);

Download files from the azure data lake

I upload my files in azure data lake. I try to download that file through asp.net mvc application.I have adl path for that file. I can download below 150 MB files. But i can't download the more then 150 MB files. Time out error came.
My Code in the bellow...
public ActionResult Download(string adlpath)
{
String header = adlpath;
Console.WriteLine(header);
string[] splitedStr = header.Split('/');
var path = GenerateDownloadPaths(adlpath);
string filename = path["fileName"];
HttpResponseMessage val = DataDownloadFile(path["fileSrcPath"]);
byte[] filedata = val.Content.ReadAsByteArrayAsync().Result;
string contentType = MimeMapping.GetMimeMapping(filename);
var cd = new System.Net.Mime.ContentDisposition
{
FileName = filename,
Inline = true,
};
Response.AppendHeader("Content-Disposition", cd.ToString());
return File(filedata, contentType);
}
public HttpResponseMessage DataDownloadFile(string srcFilePath)
{
string DownloadUrl = "https://{0}.azuredatalakestore.net/webhdfs/v1/{1}?op=OPEN&read=true";
var fullurl = string.Format(DownloadUrl, _datalakeAccountName, srcFilePath);
using (var client = new HttpClient())
{
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _accesstoken.access_token);
using (var formData = new MultipartFormDataContent())
{
resp = client.GetAsync(fullurl).Result;
}
}
return resp;
}
Image :

You should modify your code to use async and await. Your implementation blocks while retrieving the file and that is probably what times out:
public async Task<HttpResponseMessage> DataDownloadFile(string srcFilePath)
{
string DownloadUrl = "https://{0}.azuredatalakestore.net/webhdfs/v1/{1}?op=OPEN&read=true";
var fullurl = string.Format(DownloadUrl, _datalakeAccountName, srcFilePath);
using (var client = new HttpClient())
{
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _accesstoken.access_token);
using (var formData = new MultipartFormDataContent())
{
resp = await client.GetAsync(fullurl);
}
}
return resp;
}
The return value of the method is changed to Task<HttpResponseMessage> and the async modifier is added.
Calling client.GetAsync is changed to use await instead of blocking by retrieving the Result property.
Your code may still timeout. I believe that there is a configurable limit on how long a request can take before it is aborted and if you still get a timeout you should investigate this.

Per my understanding, you could try to increase the HttpClient.Timeout (100 seconds by default) for your HttpClient instance.
HttpClient.Timeout
Gets or sets the timespan to wait before the request times out.
The default value is 100,000 milliseconds (100 seconds).
Moreover, if you host your application via Azure Web App, you may encounter an idle timeout setting of 4 minutes from Azure Load Balancer. You could change the idle timeout setting in Azure VM and Azure Cloud Service. Details you could follow here.

Sending HTTP post request in C# to Microsoft Bing speech API

I am trying to send a HTTP post request to microsoft Bing speech API o transcribe an audio file. First we need to send a post request to get an "access token" as a response, then this token is used (as authorisation" in another post request to upload the actual file and get the transcription in the response. I can send the first post request and successfully get the access token, but I am not able to get a reasonable response for my second post request. I follow this page: https://www.microsoft.com/cognitive-services/en-us/speech-api/documentation/api-reference-rest/bingvoicerecognition
This is the second post request:
Guid requestId = Guid.NewGuid();
var Uri = #"https://speech.platform.bing.com/recognize?version=3.0&requestid=" + requestId.ToString() + #"&appID=D4D52672-91D7-4C74-8AD8-42B1D981415A&format=json&locale=en-US&device.os=Windows%20OS&scenarios=ulm&instanceid=f1efbd27-25fd-4212-9332-77cd63176112";
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, Uri);
request.Headers.Add("Authorization", String.Format("Bearer {0}", accessToken));
request.Headers.TryAddWithoutValidation("Content-Type", #"audio/wav; samplerate=16000");
MemoryStream ms = new MemoryStream();
using (var fs = System.IO.File.OpenRead("audio.wav"))
{
byte[] buffer = new byte[1024 * 8];
while (fs.Read(buffer, 0, buffer.Length) > 0)
{
ms.Write(buffer, 0, buffer.Length);
}
fs.Close();
}
ms.Seek(0, SeekOrigin.Begin);
HttpContent _Body = new StreamContent(ms);
request.Content = _Body;
var client2 = new HttpClient();
var response2 = client2.SendAsync(request);
I guess the problem is where I set the "Content-Type" for the header. The reason is when I debug, I don't see this property being set in the Header of the request. In fact, there is no Content-Type in the header. Any help would be appreciated. This page, which talks about the equivalent curl command, can also be helpful: https://social.msdn.microsoft.com/Forums/en-US/ad73e4f1-e576-4080-9fe7-060cc2f583ca/microsoft-bing-voice-recognition-api-authorization-404resource-not-found?forum=SpeechService

Content-Type is a content related header. The following code works for me:
public async Task<string> SendRequestAsync(string url, string bearerToken, string contentType, string fileName)
{
var content = new StreamContent(File.OpenRead(fileName));
content.Headers.TryAddWithoutValidation("Content-Type", contentType);
using (var httpClient = new HttpClient())
{
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", bearerToken);
var response = await httpClient.PostAsync(url, content);
return await response.Content.ReadAsStringAsync();
}
}
The invocation in your case (if you work in synchronous context):
var result = SendRequestAsync(Uri, accessToken, "audio/wav; samplerate=16000", "audio.wav").Result;

You can send the following header instead, to not have to do 2 requests because of the token.
If you want to not have to login each time instead of using the 'Authorization': 'Bearer {TOKEN}' header you could use the 'Ocp-Apim-Subscription-Key': '{YOUR AZURE TOKEN}' in order to not have to make a authorisation factory or more requests than necessary to the application and make it faster
NOTE: {TOKEN} is a JWT token like
eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzY29wZSI6Imh0dHBzOi8vc3BlZWNoLnBsYXRmb3JtLmJpbmcuY29tIiwic3Vic2NyaXB0aW9uLWlkIjoiZmFhZTNlYTkxNmI1NGMxZWEyODY4MDlhYTg3ZWE1MmUiLCJwcm9kdWN0LWlkIjoiQmluZy5TcGVlY2guUHJldmlldyIsImNvZ25pdGl2ZS1zZXJ2aWNlcy1lbmRwb2ludCI6Imh0dHBzOi8vYXBpLmNvZ25pdGl2ZS5taWNyb3NvZnQuY29tL2ludGVybmFsL3YxLjAvIiwiYXp1cmUtcmVzb3VyY2UtaWQiOiIiLCJpc3MiOiJ1cm46bXMuY29nbml0aXZlc2VydmljZXMiLCJhdWQiOiJ1cm46bXMuc3BlZWNoIiwiZXhwIjoxNTAwODgxNjIzfQ.KdlCrIJ_H0jxs1yyeyYxYR7ucbLuFKT__ep7lGJmGbU
NOTE2: {YOUR AZURE TOKEN} is like d5kals90935b40809dc6k38533c21e85 and you find it here
The request would look like this:
curl -v -X POST "https://speech.platform.bing.com/speech/recognition/interactive/cognitiveservices/v1?language=es-ES&locale=es-ES&format=simple&requestid=req_id" -H "Ocp-Apim-Subscription-Key: d5kals90935b40809dc6k38533c21e85" -H 'Transfer-Encoding: chunked' -H 'Content-type: audio/wav; codec="audio/pcm"; samplerate=8000' --data-binary #"{BINAYFILE}.wav"

How to get the file size from http headers

I want to get the size of an http:/.../file before I download it. The file can be a webpage, image, or a media file. Can this be done with HTTP headers? How do I download just the file HTTP header?

Yes, assuming the HTTP server you're talking to supports/allows this:
public long GetFileSize(string url)
{
long result = -1;
System.Net.WebRequest req = System.Net.WebRequest.Create(url);
req.Method = "HEAD";
using (System.Net.WebResponse resp = req.GetResponse())
{
if (long.TryParse(resp.Headers.Get("Content-Length"), out long ContentLength))
{
result = ContentLength;
}
}
return result;
}
If using the HEAD method is not allowed, or the Content-Length header is not present in the server reply, the only way to determine the size of the content on the server is to download it. Since this is not particularly reliable, most servers will include this information.

Can this be done with HTTP headers?
Yes, this is the way to go. If the information is provided, it's in the header as the Content-Length. Note, however, that this is not necessarily the case.
Downloading only the header can be done using a HEAD request instead of GET. Maybe the following code helps:
HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://example.com/");
req.Method = "HEAD";
long len;
using(HttpWebResponse resp = (HttpWebResponse)(req.GetResponse()))
{
len = resp.ContentLength;
}
Notice the property for the content length on the HttpWebResponse object – no need to parse the Content-Length header manually.

Note that not every server accepts HTTP HEAD requests. One alternative approach to get the file size is to make an HTTP GET call to the server requesting only a portion of the file to keep the response small and retrieve the file size from the metadata that is returned as part of the response content header.
The standard System.Net.Http.HttpClient can be used to accomplish this. The partial content is requested by setting a byte range on the request message header as:
request.Headers.Range = new RangeHeaderValue(startByte, endByte)
The server responds with a message containing the requested range as well as the entire file size. This information is returned in the response content header (response.Content.Header) with the key "Content-Range".
Here's an example of the content range in the response message content header:
{
"Key": "Content-Range",
"Value": [
"bytes 0-15/2328372"
]
}
In this example the header value implies the response contains bytes 0 to 15 (i.e., 16 bytes total) and the file is 2,328,372 bytes in its entirety.
Here's a sample implementation of this method:
public static class HttpClientExtensions
{
public static async Task<long> GetContentSizeAsync(this System.Net.Http.HttpClient client, string url)
{
using (var request = new System.Net.Http.HttpRequestMessage(System.Net.Http.HttpMethod.Get, url))
{
// In order to keep the response as small as possible, set the requested byte range to [0,0] (i.e., only the first byte)
request.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue(from: 0, to: 0);
using (var response = await client.SendAsync(request))
{
response.EnsureSuccessStatusCode();
if (response.StatusCode != System.Net.HttpStatusCode.PartialContent)
throw new System.Net.WebException($"expected partial content response ({System.Net.HttpStatusCode.PartialContent}), instead received: {response.StatusCode}");
var contentRange = response.Content.Headers.GetValues(#"Content-Range").Single();
var lengthString = System.Text.RegularExpressions.Regex.Match(contentRange, #"(?<=^bytes\s[0-9]+\-[0-9]+/)[0-9]+$").Value;
return long.Parse(lengthString);
}
}
}
}

WebClient webClient = new WebClient();
webClient.OpenRead("http://stackoverflow.com/robots.txt");
long totalSizeBytes= Convert.ToInt64(webClient.ResponseHeaders["Content-Length"]);
Console.WriteLine((totalSizeBytes));

HttpClient client = new HttpClient(
new HttpClientHandler() {
Proxy = null, UseProxy = false
} // removes the delay getting a response from the server, if you not use Proxy
);
public async Task<long?> GetContentSizeAsync(string url) {
using (HttpResponseMessage responce = await client.GetAsync(url))
return responce.Content.Headers.ContentLength;
}