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HTTP error 403 if POST is not used

I am trying to send protobuf data via REST from c# winform application. When I use the HTTP request with POST method( as shown in code below) it works perfect and returns "OK" status.
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://xxxxx.execute-api.eu-west-1.amazonaws.com/test/input");
request.Headers["Authorization"] = "xxxyyyzzz"
request.Method = "POST";
request.ContentType = "application/octet-stream";
byte[] bytes = System.IO.File.ReadAllBytes("C:\\MyProtobuf.proto");
request.ContentLength = bytes.Length;
Stream requestStream = request.GetRequestStream();
requestStream.Write(bytes, 0, bytes.Length);
HttpWebResponse myHttpWebResponse = (HttpWebResponse)request.GetResponse();
MessageBox.Show(myHttpWebResponse .StatusCode.ToString());
myHttpWebResponse .Close();
But if I simply want to check if website is alive or not using below code it gives me 403. Forbidden error.
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://xxxxx.execute-api.eu-west-1.amazonaws.com/test/input");
request.Headers["Authorization"] = "xxxyyyzzz";
HttpWebResponse myHttpWebResponse = (HttpWebResponse)request.GetResponse();
MessageBox.Show(myHttpWebResponse .StatusCode.ToString());
myHttpWebResponse .Close();
what could be the possible reason for this error ?

your services serves POST method verb so you must call this service with post method, otherwise you should change your service methods to support get method.

HttpWebRequest returns (400) Bad Request

The request gives the following error:
The remote server returned an error: (400) Bad Request.
I cann't find a solution on internet. Does anyone knows how to solve this?
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(#"https://maps.googleapis.com/maps/api/geocode/json");
request.ContentType = "application/x-www-form-urlencoded";
request.Method = "POST";
var parameters = string.Format("language={0}&latlng={1}&client={2}&signature={3}", "nl", "51.123456,5.612345", "gme-aa", "******_******=");
byte[] byteArray = Encoding.UTF8.GetBytes(parameters);
request.ContentLength = byteArray.Length;
Stream dataStream = request.GetRequestStream();
dataStream.Write(byteArray, 0, byteArray.Length);
dataStream.Close();
/*
* Read HttpWeb Response
*/
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
dataStream = response.GetResponseStream();
StreamReader reader = new StreamReader(dataStream);
string Response = reader.ReadToEnd();
response.Close();
EDIT:
I'm working inside Lowcode platform Outsystems. Outsystems creates the url inside WebRequest.Create() without the paramaters. So, I have access to webRequest object and need to pass the parameters.

You have to use HTTP "GET" Method.
In a GET request, you pass parameters as part of the query string.
HttpWebRequest request = (HttpWebRequest)WebRequest.Create($"https://maps.googleapis.com/maps/api/geocode/json?language=fr&latlng=51.123456,5.612345&key={apiKey}");
request.ContentType = "application/x-www-form-urlencoded";
request.Method = "GET";
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
string result = new StreamReader(response.GetResponseStream()).ReadToEnd();
}

According the documentation, the API is expecting a POST method and receiving the parameters in the URL and not the body.
If you are using the OutSystems platform you can use the Consume REST API functionality to easily call the web service without using code. Configure your API like this (you can copy the example JSON from the documentation page above):

Http Request not sent from android C#

Iam developing a cross platform android app in Xamarin. I want to send a request to register my device. Iam sending my DeviceId, DeviceName and EncodedAccountName i.e my email id.
But I dont get any response. I have tested the request on Postman and get a proper response.
Here is my code:
StringBuilder registerContent = new StringBuilder();
registerContent.Append("DeviceId=").Append(deviceId).Append("&");
registerContent.Append("Name=").Append(deviceName).Append("&");
registerContent.Append("EncodedAccountName‏=").Append(username);
WebRequest request = WebRequest.Create(EndPoints.RegisterDeviceEndPoint);
// Set the Method property of the request to POST.
request.Method = "POST";
// Create POST data and convert it to a byte array.
string postData = registerContent.ToString();
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
// Set the ContentType property of the WebRequest.
request.ContentType= "application/x-www-form-urlencoded";
// Set the ContentLength property of the WebRequest.
request.ContentLength = byteArray.Length;
// Get the request stream.
Stream dataStream = request.GetRequestStream();
// Write the data to the request stream.
dataStream.Write(byteArray, 0, byteArray.Length);
// Close the Stream object.
dataStream.Close();
// Get the response.
WebResponse response = request.GetResponse();// Dont get any response here
// Display the status.
System.Console.WriteLine(((HttpWebResponse)response).StatusDescription);
// Get the stream containing content returned by the server.
dataStream = response.GetResponseStream();
// Open the stream using a StreamReader for easy access.
StreamReader reader = new StreamReader(dataStream);
// Read the content.
string responseFromServer = reader.ReadToEnd();
// Display the content.
System.Console.WriteLine(responseFromServer);
// Clean up the streams.
reader.Close();
dataStream.Close();
response.Close();
return response.ToString();
Any ideas on what might me going wrong?
Thanks

This is how I notify my Web API and wait for a string response:
string myParameters = "?firstParam=" + someParam1 + "&secondParam=" + someParam2;
string url = someHTTPAddress + myParameters;
stringResponseFromWebAPI = (new WebClient()).DownloadString(url);

Using REST PUT in C#

I am working with a REST API and I am trying to do a PUT method to it. I found this code I was going to give a try:
static void Main()
{
string xml = "<xml>...</xml>";
byte[] arr = System.Text.Encoding.UTF8.GetBytes(xml);
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://localhost/");
request.Method = "PUT";
request.ContentType = "text/xml";
request.ContentLength = arr.Length;
Stream dataStream = request.GetRequestStream();
dataStream.Write(arr, 0, arr.Length);
dataStream.Close();
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
string returnString = response.StatusCode.ToString();
Console.WriteLine(returnString);
}
One thing I want to do if possible, and can't seem to find anything about it. I would like to pass the data of text fields so, txtEmail.Text, txtFirstName.Text, etc. Is this possible? If, so how would I go about doing this? Does this code look like it would work? Unfortunately the API I'm working with has very very little documentation. Thanks!

The code lines
Stream dataStream = request.GetRequestStream();
dataStream.Write(arr, 0, arr.Length);
dataStream.Close();
do write something to the remote website. The request stream is the way to provide data to the server, so you would create a string / object that you write to the stream to transfer to the server. In your example <xml>...</xml> is sent to the server.

HTTP POST in .NET doesn't work

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.