CurlDelegatingHandler

This package generates curl by extending HttpClient of .NET with DelegatingHandler i.e. Custom Message Handler.

GitHub link

A DelegatingHandler in .NET's HttpClient pipeline is a customizable middleware component that processes HTTP requests and responses. It allows developers to add pre-processing and post-processing logic, such as logging, authentication, retry policies, or caching. By overriding the SendAsync method, developers can create handlers that manipulate requests before passing them down the chain to other handlers or return responses directly. Multiple DelegatingHandler instances can be chained to create a sequence of processing steps, enhancing code reusability and composability. This approach enables flexible and maintainable handling of HTTP operations in .NET applications.

How it works

Any requests made with HttpClient is sent through the client pipeline containing only one message handler named CurlDelegatingHandler

The curl is returned in the response header named outputCurl.

To prevent sending request to the network (with default HttpClientHandler), the header CanSend: False should be added to the request.

Currently supported HTTP verbs are as follows

• GET
• POST
• PUT
• DELETE

Sample console application

using System.Text;
using CurlGenerator;


string url = "https://jsonplaceholder.typicode.com/posts";
string jsonPayload = @"{""title"": ""New Post"", ""body"": ""This is the body of the new post"", ""userId"": 1}";
var content = new StringContent(jsonPayload, Encoding.UTF8, "application/json");

var httpClient = new HttpClient(new CurlDelegatingHandler());
httpClient.DefaultRequestHeaders.Add(Settings.CanSend, "False");
var result = await httpClient.PostAsync(url, content);
string outputCurl = result.Headers.GetValues(Settings.OutputCurl).FirstOrDefault();
Console.WriteLine(outputCurl);

Output

curl -X POST 'https://jsonplaceholder.typicode.com/posts' -H 'Content-Type: application/json; charset=utf-8' -H 'Content-Length: 78' -d '{"title": "New Post", "body": "This is the body of the new post", "userId": 1}'

How it was tested

The test cases were inspired from Postman Code Generators.

Why is it needed

There are many online sources that tell how to convert curl to its equivalent HTTPClient code in C#. Yet, when I try to find the other way around, there's hardly any. It can be used to help debugging, log and trace incoming request.

Here is what a kind Reddit user had to tell about it.

I like it for being able to make your requests troubleshootable by another means. It can also expose what a request looks like. OP, nice work. Does a thing, does it without complication, looks like it does it well

Way Forward

• Further decouple builder methods.
• Support more Settings like Postman.

Deployment

The package has been released on nuget.org

Tech Stack

C#, .NET 8