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HttpClient.GetAsync returns weird result for some websites

Please consider this simple Code:
private async void button3_Click(object sender, EventArgs e)
{
textBox1.Text = "It begins...";
await DoAsync_Button3();
}
private async Task DoAsync_Button3()
{
HttpClient client = new HttpClient();
HttpResponseMessage response = await client.GetAsync("https://www.stackoverflow.com/");
response.EnsureSuccessStatusCode();
string responseBody = await response.Content.ReadAsStringAsync();
textBox1.Text = responseBody;
}
and the simple UI:
the problem is for some websites I got some weird result. for example: https://www.dotnetperls.com/
I got this result:
I got weird result whereas StatusCode is 200. How do I determine where the problem is? Thanks

You need to decompress the response:
HttpClient httpClient = new HttpClient(new HttpClientHandler
{
AutomaticDecompression = System.Net.DecompressionMethods.All
});
string responseAsString = await httpClient.GetStringAsync("https://www.dotnetperls.com/");
Console.WriteLine(responseAsString);
If you are using .NET 5 or 6, you can use SocketsHttpHandler instead of HttpClientHandler.

PostAsync API giving Bad Gateway

I am invoking a third party POST API from my own API (again POST METHOD). The third party API is having a security key, and it is working fine on the POSTMAN tool. However, when I tries to invoke through code, I am getting error, 'Bad Gateway'. Following is the code which I tried.
public static async Task<string> GetDetailsfromThirdParty(string kszstrng)
{
string contentstring = string.Empty;
using (var client = new HttpClient())
{
string baseURL = "https://abcde.kz.in/b2/vhsearch-all";
string prms = kszstrng;// input parameters to API, in JSON Format- this is JSON String.
try
{
using (var httpClient = new HttpClient())
{
httpClient.DefaultRequestHeaders.Accept.Clear();
httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
httpClient.DefaultRequestHeaders.Add("key", "value");
client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "application/json");
byte[] messageBytes = System.Text.Encoding.UTF8.GetBytes(prms);
var content = new ByteArrayContent(messageBytes);
content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/json");
var response = await httpClient.PostAsync(baseURL, content).ConfigureAwait(false);
var result = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
contentstring = result;
}
}
catch (Exception ex)
{
string msg = ex.Message.ToString();
}
return contentstring;
}
}
I am getting error on this line:
var response = await httpClient.PostAsync(baseURL, content).ConfigureAwait(false);
While trying to execute I am getting the below error:
Not able to find out what's the issue? There is no network / Fireawall blockage. I have cross-verified with Systems Team as well.
Please suggest any issue with the code.

First of all, i recommend you to not declare the HttpClient in a using statement since this can cause a socket exhaustion (because the connections will stay open).
(see the docs for details)
Go for a static HttpClient (or use the IHttpClientFactory if you're project is .net Core).
I can't test your code since I'm not able to access this api.
But give it a try using a cleaner approach:
// static HttpClient
private static readonly HttpClient _HttpClient = new HttpClient();
// Can be used to set the baseUrl of the HttpClient from outside
public static void SetBaseUrl(Uri baseUrl)
{
_HttpClient.BaseAddress = baseUrl;
}
public static async Task<string> GetDetailsfromThirdParty(string kszstrng)
{
string contentstring = string.Empty;
string baseURL = "https://abcde.kz.in/b2/vhsearch-all";
string prms = kszstrng; // input parameters to API, in JSON Format- this is JSON String.
try
{
// Be aware of which headers you wanna clean if using the static HttpClient
_HttpClient.DefaultRequestHeaders.Accept.Clear();
_HttpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
_HttpClient.DefaultRequestHeaders.Add("key", "value");
_HttpClient.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "application/json");
byte[] messageBytes = Encoding.UTF8.GetBytes(prms);
var content = new ByteArrayContent(messageBytes);
content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
var response = await _HttpClient.PostAsync(baseURL, content).ConfigureAwait(false);
if (response.IsSuccessStatusCode)
{
var result = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
contentstring = result;
}
}
catch (Exception ex)
{
// your exception handling
}
return contentstring;
}

Issue resolved. While forming the object to JSON String, there was an opening and closing angle brackets ([,]). Even though this is coming automatically while converting to JSON string, this was not accepted string at the vendor end. So I removed it and works perfectly. Thanks every one for the support.

C# How to post data with multiple POST requests through Facebook API

I've been trying to post a message along with a link, I can send one POST request, but I am not sure how would one send two.
Here's my code:
private void Button2_Click(object sender, EventArgs e)
{
using (var client = new HttpClient())
{
client.BaseAddress = new Uri("https://graph.facebook.com");
string message = "hello";
string link = "www.facebook.com"
var payload = GetPayload(new {message});
HttpResponseMessage response2 = client.PostAsync($"me/feed?access_token={TextBox1.Text}", payload).Result;
}
}
private static StringContent GetPayload(object data)
{
var json = JsonConvert.SerializeObject(data);
return new StringContent(json, Encoding.UTF8, "application/json");
}
I am not sure how can I include the link too along with the message.

Al-right it turns out that the variable link should be passed as such:
var data = {message, link}
Thanks to chetan.

Xamarin Forms Post Request Http Issue

I'm working on making a POST request using my Xamarin form to send data to an Action in my controller in my WebAPI project. The code with breakpoints doesn't go beyond
client.BaseAddress = new Uri("192.168.79.119:10000");
I have namespace System.Net.Http and using System mentioned in the code.
private void BtnSubmitClicked(object sender, EventArgs eventArgs)
{
System.Threading.Tasks.Task<HttpResponseMessage> statCode = ResetPassword();
App.Log(string.Format("Status Code", statCode));
}
public async Task<HttpResponseMessage> ResetPassword()
{
ForgotPassword model = new ForgotPassword();
model.Email = Email.Text;
var client = new HttpClient();
client.BaseAddress = new Uri("192.168.79.119:10000");
var content = new StringContent(
JsonConvert.SerializeObject(new { Email = Email.Text }));
HttpResponseMessage response = await client.PostAsync("/api/api/Account/PasswordReset", content); //the Address is correct
return response;
}
Need a way to make a Post request to that Action and sending that String or the Model.Email as a parameter.

You need to use a proper Uri and also await the Task being returned from the called method.
private async void BtnSubmitClicked(object sender, EventArgs eventArgs) {
HttpResponseMessage response = await ResetPasswordAsync();
App.Log(string.Format("Status Code: {0}", response.StatusCode));
}
public Task<HttpResponseMessage> ResetPasswordAsync() {
var model = new ForgotPassword() {
Email = Email.Text
};
var client = new HttpClient();
client.BaseAddress = new Uri("http://192.168.79.119:10000");
var json = JsonConvert.SerializeObject(model);
var content = new StringContent(json, System.Text.Encoding.UTF8, "application/json");
var path = "api/api/Account/PasswordReset";
return client.PostAsync(path, content); //the Address is correct
}

Testing REST API endpoints

I have a number of REST api endpoints that I am calling via ajax from a web client, and I want to write some automated tests to insure that they work properly outside of a web browser.
I am writing them as unit tests Tests and here is what I have so far:
[TestClass]
public class ApiTests
{
string local_host_address = "http://localhost:1234//";
public async Task<string> Post(string path, IEnumerable<KeyValuePair<string, string>> parameters)
{
using (var client = new HttpClient())
{
client.Timeout = new TimeSpan(0,0,5);
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
var response_message = await client.PostAsync(local_host_address + path, new FormUrlEncodedContent(parameters));
var response = await response_message.Content.ReadAsStringAsync();
if (response_message.IsSuccessStatusCode)
{
return response;
}
else
{
throw new Exception("Request failed");
}
}
}
[TestMethod]
[TestCategory("ApiTests")]
public void TestLogon()
{
var parameters = new Dictionary<string, string>();
parameters["email"] = "bob#aol.com";
parameters["password"] = "rosebud";
Task.Run( () =>
{
var output = Post("Default.aspx/Logon", parameters);
Console.WriteLine(output.Result);
}).Wait();
}
}
...pretty basic, it just tries to call a specific endpoint, and return the results. Problem is, this call returns the basic default.aspx web page body, not the results generated by default.aspx/logon. I am doing something wrong, but I have been over it with a debugger and I cannot see my error. The default.aspx/logon endpoint exists and it works perfectly when I access it via website. Am I missing or overlooking something?
-TTM
SOLUTION:
Bruno's alteration of my code snippet works quite nicely. Anyone else trying to solve the problem of testing a REST endpoint can just put that into a unit test and pass in a POCO and it will return the JSON response.

You are sending the body as FormUrlEncoded although you marked your request as application/json.
If your API is REST and takes JSON, instead of taking the Dictionary, you could deserialize an object (e.g. with Newtonsoft.Json):
public async Task<string> Post<T>(string path, T data)
{
using (var client = new HttpClient())
{
client.Timeout = new TimeSpan(0, 0, 5);
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
var json = JsonConvert.SerializeObject(data);
var response_message = await client.PostAsync(local_host_address + path, new StringContent(json, Encoding.UTF8, "application/json");
var response = await response_message.Content.ReadAsStringAsync();
if (response_message.IsSuccessStatusCode)
{
return response;
}
else
{
throw new Exception("Request failed");
}
}
}