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What is the correct way to handle to read output of web api stream from c# client

[HttpGet]
[Route("stream/{filePath}")]
public System.IO.Stream ReadStreamFromFile(string filePath)
{
return new System.IO.MemoryStream(System.IO.File.ReadAllBytes(filePath));
}
Now I wanto to know how to read stream in C# client which is a generic way to get output and as currently supports string type.
// Get response
using (HttpWebResponse webresponse = request.GetResponse() as HttpWebResponse)
{
// Get the response stream
StreamReader responseStream = new StreamReader(webresponse.GetResponseStream());
response = responseStream.ReadToEnd();
}
Please suggest.
Regards,
amaR

You can use HttpClient for sending request and then get the response as stream like this:
var client= new HttpClient();
var response= await client.GetAsync("url");
var stream= await response.Content.ReadAsStreamAsync();
By the way, for using HttpClient I recommend to read this: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/http-requests?view=aspnetcore-6.0

byte[] byteArray = Encoding.ASCII.GetBytes( test );
MemoryStream stream = new MemoryStream( byteArray );
By using above code, you will be able to get stream.

Use C# to Save an Excel File Contained in a Tableau API Response

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();

Mapping JSON from Yahoo! Finance API to C# objects [duplicate]

This question already has answers here:
Deserialize JSON data with C#
(4 answers)
Closed 1 year ago.
I am a student working on a project. I am trying to use the Yahoo! Finance API as a source for my data https://www.yahoofinanceapi.com . I can use HttpWebRequests to call the API and get the "OK" code, see the code below on how I did it:
string BaseURL = "https://yfapi.net/v6/finance/quote?symbols=AAPL";
string addSymbol = "%2C";
string URL = BaseURL;
foreach (string stock in stocks)
{
URL += addSymbol + stock;
}
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
request.Headers.Add("X-API-KEY", "[My API key]");
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Console.WriteLine(response.ContentType);
Console.WriteLine(response.StatusCode);
response.ContentType gives back "application/json".
response.StatusCode gives back "OK".
Since the response is a JSON I tried to parse it into a string using .ToString() but this obviously doesn't work. When I print it, it just says "System.Net.HttpWebResponse" instead of the showing the actual data in the JSON.
After that I tried to deserialize it using newtonsoft
Results result = JsonConvert.DeserializeObject<Results>(request.GetResponse().ToString());
where Results is a class I made where there is a list of stocks, Stock is also a class I made with some variables in it with the same names of variables in the JSON response.
I got a JSON response from PostMan when I tested the API, opened the response to see what kind of data it contained.
When I ran my code I got the following error message:
Newtonsoft.Json.JsonReaderException: 'Unexpected character encountered while parsing value: S. Path '', line 0, position 0.'
This was as far as I got, I tested a few other methods trying to get this working but this one worked the "best".
My biggest issue at the moment is mapping the response into a c# object.
Anything that can help me understand is appreciated :D

You're trying to serialise the HttpWebResponse object into Results, which means deserialisation won't work.
The data is still wrapped & won't be in the format of the Results object.
The GetResponseStream() method can be used to get the contents of the HTTP response as a stream, which can then be deserialised directly, in this case, using Json.NET.
Replace this section:
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Console.WriteLine(response.ContentType);
Console.WriteLine(response.StatusCode);
With this:
var serializer = new JsonSerializer();
using (var response = (HttpWebResponse)request.GetResponse())
{
var encoding = Encoding.GetEncoding(response.CharacterSet);
using var responseStream = response.GetResponseStream();
using var reader = new StreamReader(responseStream, encoding);
using (var jsonTextReader = new JsonTextReader(reader))
{
Console.WriteLine(response.ContentType);
Console.WriteLine(response.StatusCode);
Results result = serializer.Deserialize<Results>(jsonTextReader);
}
}
Alternatively, a much better solution if you're using .NET 4.5 <= would be to use HttpClient like below:
private static readonly HttpClient httpClient = new HttpClient();
...
string BaseURL = "https://yfapi.net/v6/finance/quote?symbols=AAPL";
string addSymbol = "%2C";
string URL = BaseURL;
foreach(string stock in stocks) {
URL += addSymbol + stock;
}
client.DefaultRequestHeaders.Add("X-API-KEY", "[My API key]");
var data = await httpClient.GetStringAsync(address);
Results result = JsonConvert.DeserializeObject<Results>(data);

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

C# httpwebrequest blank chars in responsestream

I'm trying to read the reponse from a webserver using httpwebrequests in C#.
I use the following code:
UriBuilder urib = new UriBuilder();
urib.Host = "wikipedia.com";
HttpWebRequest req = WebRequest.CreateHttp(urib.Uri);
req.KeepAlive = false;
req.Host = "wikipedia.com/";
req.Method = "GET";
HttpWebResponse response = (HttpWebResponse) req.GetResponse();
byte[] buffer = new byte[response.ContentLength];
System.IO.Stream stream = response.GetResponseStream();
stream.Read(buffer, 0, buffer.Length);
Console.WriteLine(System.Text.Encoding.ASCII.GetString(buffer, 0, buffer.Length));
The code does indeed retrieve the correct amount of data (I compared the contentlength used to create the buffer, with the length of the console output, they're the same.
My problem is that the last 80% or so of the response is blank chars. They're all 0x00.
I tested this with several pages, including wikipedia.com and it just cuts off mid-file for some reason.
Have I misunderstood/misused the way to use webrequests or can anyone spot an error here?

Try to use this method:
public static String GetResponseString(Uri url, CookieContainer cc)
{
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
request.Method = WebRequestMethods.Http.Get;
request.CookieContainer = cc;
request.AutomaticDecompression = DecompressionMethods.GZip;
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
StreamReader reader = new StreamReader(response.GetResponseStream());
String responseString = reader.ReadToEnd();
response.Close();
return responseString;
}

There are a couple of issues with your code:
Your trying to read the entire response in one go using Stream.Read - that's not what it was designed for. This should be used for more optimal reading e.g. 4KB chunks.
Your reading a HTML response as ASCII encoding - are you sure the page doesn't contain any Unicode characters? I would stick to UTF-8 encoding to be on the safe side (or alternatively read the Content-Type header in the response).
When reading characters from a byte stream (which is what your response is essentially) the recommended approach is to use StreamReader. More specifically, if you want to read the entire stream in one go then use StreamReader.ReadToEnd.
Your code could be shortened to:
HttpWebRequest req = WebRequest.CreateHttp(new Uri("http://wikipedia.org"));
req.Method = WebRequestMethods.Http.Get;
using (var response = (HttpWebResponse)req.GetResponse())
using (var reader = new StreamReader(response.GetResponseStream()))
{
Console.WriteLine(reader.ReadToEnd());
}