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
Related
I'm trying to download an Excel file from a Tableau view, using a snippet based on this article: Downloading Files with the WebRequest and WebResponse Classes.
WebResponse response = null;
Stream webStream = null;
Stream localStream = null;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(endPoint);
request.Method = "GET";
request.Headers.Add("X-Tableau-Auth", token);
response = request.GetResponse();
webStream = response.GetResponseStream();
localStream = File.Create("testing.xlsx");
byte[] buffer = new Byte[1024];
int bytesRead;
int bytesProcessed = 0;
do
{
bytesRead = webStream.Read(buffer, 0, buffer.Length);
localStream.Write(buffer, 0, bytesRead);
bytesProcessed += bytesRead;
} while (bytesRead > 0);
response.Close();
webStream.Close();
localStream.Close();
But when I try to open the Excel file it says "Nope, maybe it is corrupt?". The response is a complete Excel file "ready to be saved", which means that it's encoded using UTF-8. Indeed, if I use Postman to do the call, and then save the response, it's saved and opens without any problem.
Before finding the page I said above, I thought the problem was because the response is UTF-8 and the class String is UTF-16. So, I made some testing getting the data from the file generated by Postman and then writing to a new file. The result of the testings: indeed, if the data passes through a String, it's not well saved. Then I tried with that code, and got the same result: fail. I'm pretty sure this code is not using any UTF-16 encoding variable, but maybe I'm wrong.
Anyway, do anyone knows what is my problem with that code, or point me to the right way to accomplish my task? That is, to download a Tableau report to Excel, using the Tableau API.
Thanks in advance.
Unless you're stuck on a particularly old version of .NET, that referenced link is from 2004. The following code will work in .NET 5 / C# 9, and in earlier versions with just some minor tweaking of the using statements. It's showing for Tableau Online, but should work fine for recent versions of Server, if I had to guess. This is sample-grade code, so I would recommend following best practices for the HttpClient if you intend to make this call frequently.
//using System.IO;
//using System.Net.Http;
var token = "your-session-token";
var uri = "https://your-pod.online.tableau.com/api/.../sites/.../views/.../crosstab/excel";
var yourFile = "D:/file/test.xlsx";
using var client = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Get, uri);
request.Headers.Add("X-Tableau-Auth", token);
using var response = await client.SendAsync(request);
using FileStream outputFileStream = new FileStream(yourFile, FileMode.Create);
await response.Content.CopyToAsync(outputFileStream);
UPDATE: If you're constrained to WebRequest and non-async methods, you can try the following:
var token = "your-session-token";
var uri = "https://your-pod.online.tableau.com/api/.../sites/.../views/.../crosstab/excel";
var yourFile = "D:/file/test.xlsx";
WebRequest request = WebRequest.Create(uri);
request.Method = "GET";
request.Headers.Add("X-Tableau-Auth", token);
var response = request.GetResponse();
if(((HttpWebResponse)response).StatusCode == HttpStatusCode.OK)
{
using (Stream dataStream = response.GetResponseStream())
using (FileStream fileStream = new FileStream(yourFile, FileMode.CreateNew))
{
dataStream.CopyTo(fileStream);
}
}
response.Close();
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);
I'm trying to migrate a Windows C# library to Windows Phone 8 and I'm forced to make some changes in how the library gets data from an online URI.
I'm using the BCL's HttpClient to perform my data retrieval and everything's fine for now.
The library also requires an upload feature, and I can't find a way to do this using th HttpClient.
Here's the code:
// Client setup
var httpclient = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Post, string.Format(SubmitURI, value));
// Add the headers
request.Headers.Add("header", header);
var postData = GetPostData();
var data = Encoding.UTF8.GetBytes(postData);
// Side question -> Content is null here!
request.Content.Headers.Add("ContentType", "multipart/form-data; boundary=" + Boundary);
// BEGIN ORIGINAL CODE
var stream = request.GetRequestStream();
stream.Write(data, 0, data.Length);
stream.Close();
// END ORIGINAL CODE
// Get response
var response = await httpclient.SendAsync(request);
var responseContent = new StreamReader(await response.Content.ReadAsStreamAsync()).ReadToEnd();
Between the BEGIN ORIGINAL CODE and END ORIGINAL CODE comments, there's the code that I'm not able to migrate, so that you can understand what it does and I may need to make it work on WP.
The other of the code is already working on WP, except for the
request.Content.Headers.Add("ContentType", "multipart/form-data; boundary=" + Boundary);
because, for some reasons, request.Content is null.
So my question is: how can I migrate those 3 lines to WP using HttpClient (or any better way)?
And, as a little side question, why is request.Content null?
EDIT: based on #Johan van der Slikke's answer I've edited my code. It compiles, but the server reports that no file was uploaded, so I guess that there are still some issues.
var stream = new MemoryStream(data);
var streamContent = new StreamContent(stream);
request.Content = streamContent;
request.Content.Headers.Add("ContentType", "multipart/form-data; boundary=" + Boundary);
// Get response
var response = await httpclient.SendAsync(request);
You should wrap your stream in the StreamContent class (a subclass of HttpContent) and send it with the HttpClient using the PostAsync or PutAsync methods.
Edit
You don't need to use HttpRequestMessage.
var stream = new MemoryStream(data);
var streamContent = new StreamContent(stream);
// Get response
var response = await httpclient.PostAsync(streamContent)
Also you don't need to create a MemoryStream with your byte array. You can wrap it in a ByteArrayContent directly.
var response = await httpclient.PostAsync(new ByteArrayContent(data))
Maybe (because I see you using multipart/form-data header) you should use MultipartFormDataContent classes or FormUrlEncodedContentClasses.
You can send multi-part content like this,
var client = new HttpClient();
var content = new MultipartContent();
content.Add(new ByteArrayContent(data));
var response = await client.PostAsync(SubmitUrl, content);
However, I am curious what media type your "PostData" is. You may want to set the content-type header on the ByteArrayContent.
What would a be a Java equivalent to the following
// C#
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
String responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();
....
}
Currently I have
//Java
HttpResponse response = httpclient.execute(request);
InputStream responseBody = response.getEntity().getContent();
Apache's http client, which I think you're using, comes with a EntityUtils class for getting the string from a method.
This method using the character encoding specified in the response. There are overloads available if different encodings are required.
HttpResponse response = httpclient.execute(request);
String responseString = EntityUtils.toString(response.getEntity);
This might be a little long, but if you didn't want to use 3rd party libraries you could do this:
InputStream stream = new FileInputStream("file");
byte[] b = new byte[stream.available()];
stream.read(b);
String file = new String(b);
I've got a problem with creating an HTTP post request in .NET. When I do this request in ruby it does work.
When doing the request in .NET I get following error:
<h1>FOXISAPI call failed</h1><p><b>Progid is:</b> carejobs.carejobs
<p><b>Method is:</b> importvacature/
<p><b>Parameters are:</b>
<p><b> parameters are:</b> vacature.deelnemernr=478
</b><p><b>GetIDsOfNames failed with err code 80020006: Unknown name.
</b>
Does anyone knows how to fix this?
Ruby:
require 'net/http'
url = URI.parse('http://www.carejobs.be/scripts/foxisapi.dll/carejobs.carejobs.importvacature')
post_args = {
'vacature.deelnemernr' => '478',
}
resp, data = Net::HTTP.post_form(url, post_args)
print resp
print data
C#:
Uri address = new Uri(url);
// Create the web request
HttpWebRequest request = WebRequest.Create(address) as HttpWebRequest;
// Set type to POST
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
// Create the data we want to send
StringBuilder data = new StringBuilder();
data.Append("vacature.deelnemernr=" + HttpUtility.UrlEncode("478"));
// Create a byte array of the data we want to send
byte[] byteData = UTF8Encoding.UTF8.GetBytes(data.ToString());
// Set the content length in the request headers
request.ContentLength = byteData.Length;
// Write data
using (Stream postStream = request.GetRequestStream())
{
postStream.Write(byteData, 0, byteData.Length);
}
// Get response
using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
{
// Get the response stream
StreamReader reader = new StreamReader(response.GetResponseStream());
// Console application output
result = reader.ReadToEnd();
}
return result;
Don't you need the ? after the URL in order to do a post with parameters? I think that Ruby hides this behind the scenes.
I found the problem! The url variable in the C# code was "http://www.carejobs.be/scripts/foxisapi.dll/carejobs.carejobs.importvacature/"
It had to be "http://www.carejobs.be/scripts/foxisapi.dll/carejobs.carejobs.importvacature" without the backslash.