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How to Use curl in .NET 10 (C#)

#csharp #dotnet #linux #tutorial

How to Use curl in .NET (C#)

If you've ever worked with APIs, you've probably seen curl commands in documentation. curl is the universal tool for making HTTP requests from the command line. But what if you want to use those same requests in your C# application?

Traditional approaches require translating curl commands into HttpClient code, which can be tedious and error-prone. But there's a better way: CurlDotNet lets you paste curl commands directly into C# code.

Installing CurlDotNet

First, add the NuGet package to your project:

dotnet add package CurlDotNet
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Or via Package Manager Console in Visual Studio:

Install-Package CurlDotNet
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Or add it directly to your .csproj file:

<ItemGroup>
  <PackageReference Include="CurlDotNet" Version="1.0.0" />
</ItemGroup>
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Basic Usage

The simplest way to use CurlDotNet is to paste a curl command as a string:

using CurlDotNet;
using System;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        // Simple GET request
        var result = await Curl.ExecuteAsync(
            "curl https://api.github.com/users/octocat"
        );

        Console.WriteLine($"Status: {result.StatusCode}");
        Console.WriteLine($"Body: {result.Body}");
    }
}
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That's it! The curl command is executed and you get a CurlResult object back with the response.

Working with Different HTTP Methods

GET Requests 

var result = await Curl.ExecuteAsync(
    "curl https://jsonplaceholder.typicode.com/posts/1"
);

var post = result.ParseJson<Post>();
Console.WriteLine($"Title: {post.Title}");
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POST Requests 

var result = await Curl.ExecuteAsync(@"
  curl -X POST https://jsonplaceholder.typicode.com/posts \
    -H 'Content-Type: application/json' \
    -d '{
      \"title\": \"My Post\",
      \"body\": \"This is the content\",
      \"userId\": 1
    }'
");

if (result.IsSuccess)
{
    var newPost = result.ParseJson<Post>();
    Console.WriteLine($"Created post ID: {newPost.Id}");
}
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PUT Requests 

var result = await Curl.ExecuteAsync(@"
  curl -X PUT https://jsonplaceholder.typicode.com/posts/1 \
    -H 'Content-Type: application/json' \
    -d '{
      \"title\": \"Updated Title\",
      \"body\": \"Updated content\",
      \"userId\": 1
    }'
");
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DELETE Requests 

var result = await Curl.ExecuteAsync(
    "curl -X DELETE https://jsonplaceholder.typicode.com/posts/1"
);

if (result.StatusCode == 200)
{
    Console.WriteLine("Post deleted successfully");
}
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Adding Headers

Headers are added with the -H or --header flag:

var result = await Curl.ExecuteAsync(@"
  curl https://api.github.com/user \
    -H 'Accept: application/vnd.github.v3+json' \
    -H 'Authorization: token YOUR_GITHUB_TOKEN' \
    -H 'User-Agent: MyApp/1.0'
");
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Authentication

Basic Authentication 

var result = await Curl.ExecuteAsync(
    "curl -u username:password https://api.example.com/protected"
);
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Bearer Token 

var result = await Curl.ExecuteAsync(@"
  curl https://api.example.com/protected \
    -H 'Authorization: Bearer YOUR_TOKEN'
");
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Working with JSON

CurlDotNet makes JSON handling easy:

// Send JSON
var result = await Curl.ExecuteAsync(@"
  curl -X POST https://api.example.com/users \
    -H 'Content-Type: application/json' \
    -d '{\""name\"":\""John\"",\""email\"":\""john@example.com\""}'
");

// Parse JSON response
var user = result.ParseJson<User>();

// Or use the dynamic API
dynamic dynamicUser = result.AsJsonDynamic();
Console.WriteLine(dynamicUser.name);
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File Operations

Downloading Files 

// Download and save to file
var result = await Curl.ExecuteAsync(
    "curl -o image.png https://example.com/image.png"
);

// The file is saved automatically, but you can also access it in memory
Console.WriteLine($"Downloaded {result.BinaryData.Length} bytes");
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Uploading Files 

var result = await Curl.ExecuteAsync(@"
  curl -X POST https://api.example.com/upload \
    -F 'file=@/path/to/document.pdf' \
    -F 'description=My Document' \
    -H 'Authorization: Bearer YOUR_TOKEN'
");
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Handling Responses

The CurlResult object provides many useful properties and methods:

var result = await Curl.ExecuteAsync(
    "curl https://api.example.com/data"
);

// Check if successful (200-299)
if (result.IsSuccess)
{
    // Get status code
    Console.WriteLine($"Status: {result.StatusCode}");

    // Get response body
    Console.WriteLine($"Body: {result.Body}");

    // Access headers
    var contentType = result.Headers["Content-Type"];

    // Parse JSON
    var data = result.ParseJson<DataModel>();

    // Save to file
    result.SaveToFile("output.json");
}

// Or use fluent chaining
var data = result
    .EnsureSuccess()           // Throws if not 200-299
    .SaveToFile("backup.json")
    .ParseJson<DataModel>();
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Error Handling

Handle different types of errors:

try
{
    var result = await Curl.ExecuteAsync("curl https://example.com/api");
}
catch (CurlDnsException ex)
{
    Console.WriteLine($"DNS error: {ex.Message}");
}
catch (CurlTimeoutException ex)
{
    Console.WriteLine($"Timeout: {ex.Message}");
}
catch (CurlHttpException ex)
{
    Console.WriteLine($"HTTP {ex.StatusCode}: {ex.Message}");
}
catch (CurlException ex)
{
    Console.WriteLine($"Error: {ex.Message}");
}
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Advanced Features

Following Redirects 

var result = await Curl.ExecuteAsync(
    "curl -L https://bit.ly/example"  // -L follows redirects
);
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Setting Timeouts 

var result = await Curl.ExecuteAsync(
    "curl --max-time 30 https://slow-api.example.com"
);
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Verbose Output 

var result = await Curl.ExecuteAsync(
    "curl -v https://api.example.com"  // -v shows detailed output
);
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Custom User Agent 

var result = await Curl.ExecuteAsync(
    "curl -A 'MyApp/1.0' https://api.example.com"
);
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Using the Fluent Builder API

For programmatic request building, use the fluent API:

var result = await CurlRequestBuilder
    .Post("https://api.example.com/users")
    .WithHeader("Content-Type", "application/json")
    .WithJson(new { name = "John", email = "john@example.com" })
    .WithTimeout(TimeSpan.FromSeconds(30))
    .FollowRedirects()
    .ExecuteAsync();
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Real-World Example: GitHub API

Here's a complete example working with GitHub's API:

using CurlDotNet;
using System;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        var token = Environment.GetEnvironmentVariable("GITHUB_TOKEN");

        // Get user information
        var userResult = await Curl.ExecuteAsync($@"
          curl https://api.github.com/user \
            -H 'Accept: application/vnd.github.v3+json' \
            -H 'Authorization: token {token}'
        ");

        var user = userResult.ParseJson<GitHubUser>();
        Console.WriteLine($"Logged in as: {user.Login}");
        Console.WriteLine($"Name: {user.Name}");
        Console.WriteLine($"Public repos: {user.PublicRepos}");

        // List repositories
        var reposResult = await Curl.ExecuteAsync($@"
          curl https://api.github.com/user/repos \
            -H 'Accept: application/vnd.github.v3+json' \
            -H 'Authorization: token {token}'
        ");

        var repos = reposResult.ParseJson<List<Repository>>();
        Console.WriteLine($"\nYou have {repos.Count} repositories:");
        foreach (var repo in repos)
        {
            Console.WriteLine($"  - {repo.FullName}");
        }

        // Create a new repository
        var createResult = await Curl.ExecuteAsync($@"
          curl -X POST https://api.github.com/user/repos \
            -H 'Accept: application/vnd.github.v3+json' \
            -H 'Authorization: token {token}' \
            -d '{{\""name\"":\""my-new-repo\"",\""private\"":true,\""description\"":\""Created with CurlDotNet\""}}'
        ");

        if (createResult.IsSuccess)
        {
            var newRepo = createResult.ParseJson<Repository>();
            Console.WriteLine($"\nCreated repository: {newRepo.FullName}");
        }
    }
}

public class GitHubUser
{
    public string Login { get; set; }
    public string Name { get; set; }
    public int PublicRepos { get; set; }
}

public class Repository
{
    public string Name { get; set; }
    public string FullName { get; set; }
    public bool Private { get; set; }
}
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Conclusion

CurlDotNet makes using curl commands in C# simple and natural. You can paste curl commands from documentation directly into your code without translation. This saves time, reduces errors, and makes API integration much easier.

Try it out in your next project - I think you'll find it as useful as I do!

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