C# – How to get the status code when using HttpClient

When you use HttpClient to make requests, you can directly get the status code from the HttpResponseMessage object, like this: The main reason for checking the status code is to determine if the request was successful and then reacting to error status codes (usually by throwing an exception). The HttpResponseMessage class has two helpers that … Read more

C# – How to read problem details JSON with HttpClient

Problem details (RFC7807) is a standardized error response format that has a Content-Type of application/problem+json, an error response code (i.e. 400 – Bad Request), and has a response body that looks like this: This can be extended to include any number of properties. The example shown above comes from the default way ASP.NET Core returns … Read more

C# – Handling redirects with HttpClient

HttpClient handles redirects automatically. When you send a request, if the response contains a redirect status code (3xx) and redirect location, then it’ll send a new request to the redirect location. You can turn off this auto-redirect behavior by passing in an HttpClientHandler with AllowAutoRedirect=false. This prevents it from following redirects automatically, and allows you … Read more

C# – Examples of using JsonDocument to read JSON

You can use the JsonDocument class when you want to read and process JSON without having to deserialize the whole thing to an object. For example, let’s say you have the following JSON object representing wind variables: Now let’s say you’re only interested in the wind speed. Instead of having to deserialize this into a … Read more

C# – Configuring how long an HttpClient connection will stay open

When you use a single instance of HttpClient to send requests, it keeps connections open in order to speed up future requests. By default, idle connections are closed after 2 minutes, and otherwise will be kept open forever (in theory). In reality, the connection can be closed by the server-side (or other external factors) regardless … Read more

C# – The performance gains of HttpClient reusing connections

When you use the same instance of HttpClient for multiple requests (sequential and concurrent) to the same URL, it’ll reuse connections. Requests that get to reuse a connection are 5.5-8.5x faster than requests that have to open a new connection. There are a few scenarios that benefit from this connection reuse: Sending sequential requests frequently. … Read more

C# – Disposing the request HttpContent when using HttpClient

Before .NET Core 3.0 (including .NET Framework), HttpClient disposes the request HttpContent object for you. This is surprising default behavior (a violation of the principle of least surprise for sure). This causes multiple problems, but one of the main problems is it prevents you from reusing the HttpContent object (you’re greeted with an ObjectDisposedException if … Read more

C# – How to send a file with HttpClient

In order to send a file in a request with HttpClient, add the file into a MultipartFormDataContent object, and send this object as the request content. Here’s an example: This sends the following multipart/form-data POST request: In this article, I’ll explain a few details about MultipartFormDataContent, and show a few other file-sending scenarios. MultipartFormDataContent Add() … Read more

C# – How to read response headers with HttpClient

When you send a request with HttpClient, it returns an HttpResponseMessage. You can read the response headers through the HttpResponseMessage.Headers property: This outputs the response headers: Raw response headers are really just key/value(s) pairs. When the response comes in, the headers are loaded into the Headers property (which is of type HttpResponseHeaders). This parses the … Read more

C# – How to cancel an HttpClient request

It’s a good idea to provide users with a way to cancel a HttpClient request that’s taking too long. To be able to cancel an HttpClient request, you can pass in a CancellationToken: To get a CancellationToken, you have to create a CancellationTokenSource: To actually cancel the request, you have to call CancellationTokenSource.Cancel(): This means … Read more