CurlDotNet Cookbook: curl recipes in C#

These curl recipes in C# show how to do one common HTTP task each with CurlDotNet, the pure .NET library that runs curl command strings. Every recipe gives the curl command first, the Curl.ExecuteAsync call that runs it, and the CurlRequestBuilder equivalent where one exists.

Installation

dotnet add package CurlDotNet

Package page: CurlDotNet on NuGet.

Beginner recipes

Start here if you are new to CurlDotNet. See also the beginner overview.

curl GET request in C# - fetch a URL, check the status, read headers
curl -X POST JSON in C# - -d, --json, WithJson, ParseJson<T>()
curl -d form data POST in C# - URL-encoded forms and --data-urlencode
curl -F file upload in C# - multipart/form-data, -T uploads and --data-binary
curl download file in C# (curl -o) - -o, -O, -J, -C - resume, Curl.DownloadAsync
Handle curl errors and exceptions in C# - status codes, -f, EnsureSuccess(), typed exceptions and exit codes
Call a REST API with curl in C# - bearer tokens, verbs, a reusable client

One flag at a time

curl follow redirects in C# (curl -L) - -L, --max-redirs, CurlTooManyRedirectsException
curl with cookies in C# (curl -b and -c) - cookie strings, cookie files and -c cookie jars
curl proxy in C# (curl -x and SOCKS5) - -x, --proxy-user, --noproxy, proxy environment variables, --socks5
curl timeout in C# (–max-time and –connect-timeout) - -m, --connect-timeout, no hidden default, CurlOperationTimeoutException
curl -I HEAD request in C# - headers without the body
curl PUT, DELETE and PATCH requests in C# - -X with and without a body
curl digest, NTLM and basic auth in C# - -u, --digest, --ntlm, --anyauth, .netrc, bearer tokens
curl –retry in C# - --retry, --retry-delay, --retry-max-time, WithRetries
curl -w write-out in C# - %{http_code}, %{time_total}, %{json}, output on failure
curl multiple URLs and URL globbing in C# - several URLs, {a,b}, [1-10], #1, --next
curl config files, –variable and .netrc in C# - -K, --variable, ``, -n

Quick examples

GET

using CurlDotNet;

var result = await Curl.ExecuteAsync("curl https://api.github.com/zen");   // sends User-Agent: curl/8.7.1, like curl
Console.WriteLine(result.Body);

POST JSON

using CurlDotNet;

var result = await Curl.ExecuteAsync(@"
    curl -X POST https://httpbin.org/post \
         -H 'Content-Type: application/json' \
         -d '{""name"":""Ada""}'");

Console.WriteLine(result.IsSuccess ? "created" : $"HTTP {result.StatusCode}");

Download a file

using CurlDotNet;

var result = await Curl.ExecuteAsync("curl -L -o image.png https://httpbin.org/image/png");
Console.WriteLine(result.OutputFiles[0]);

Find a recipe by task

I want to…	Recipe
Fetch data from a URL	curl GET request
Send JSON to an API	curl -X POST JSON
Submit an HTML-style form	curl -d form data
Upload a file	curl -F file upload
Save a response to disk	curl download file
Update or delete a resource	PUT, DELETE and PATCH
Log in with a username and password	digest, NTLM and basic auth
Send a session cookie	cookies
Go through a corporate proxy	proxy
Stop a slow request	timeout
Check headers without downloading	HEAD request
Follow a 301/302	follow redirects
Deal with failures	handle errors
Retry a flaky endpoint	retry
Print the status code or timing	write-out
Fetch a numbered series of URLs	multiple URLs and globbing
Keep options or credentials in a file	config files, variables and .netrc

How the recipes are written

Each page states the problem, shows the curl command and the C# that runs it, then the builder version, a few variations, the things that commonly go wrong, and links onward. Every snippet is short enough to paste into a console app with using CurlDotNet; (and using CurlDotNet.Core; for the builder and CurlResult).

CurlDotNet Cookbook: curl Recipes in C#

Copy-paste curl recipes in C# with CurlDotNet: GET, POST JSON, forms, file upload and download, redirects, cookies, proxies, timeouts, retries, write-out, globbing, config files, HEAD and auth.