x402.Client.EVM

x402-dotnet

x402 Payment Protocol implementation for .Net

Starting with version 2.0.0, this library targets x402 v2.
All 0.x versions target x402 v1.

x402 on the server

Install the x402 packages from NuGet:

• x402
• x402.Coinbase to use the Coinbase facilitator

Features:

• Add an x402-compatible paywall to any URL
• Easily use an attribute to handle payments for your API methods
• Add URLs that require payment using the middleware
• Support advanced scenarios by calling the X402Handler in your API controller
• Handle payment settlement using any remote facilitator
• Optionally use the Coinbase facilitator (with API key)
• Extensible AssetInfoProvider that fills in network and coin data based on the asset address

x402 enabled HttpClient

Install the x402.Client.EVM package from NuGet:

• x402.Client.EVM

Features:

• Transparant access x402-protected resources
• Fully HttpClient compatible
• Pay using the embedded EVM compatible wallet (Ethereum / Base)
• Set allowances per request or globally
• X402.Client.ConsoleSample sample application included
• Blazor Sample project available

How to use?

Register the x402 services and facilitator in Program.cs:

// Use the default HttpFacilitator
builder.Services.AddX402().WithHttpFacilitator(facilitatorUrl);

Use the PaymentRequired Attribute (easy to add to existing projects)

// Use the Payment Required Attribute
[HttpGet]
[Route("protected")]
[PaymentRequired("1000", "0x036CbD53842c5426634e7929541eC2318f3dCF7e", "0xYourAddressHere")]
public SampleResult Protected()
{
    return new SampleResult { Title = "Protected by PaymentRequired Attribute" };
}

Directly in an API Controller (for more control)

public ResourceController(X402HandlerV2 x402Handler)
{
    this.x402Handler = x402Handler;
}

[HttpGet]
[Route("dynamic")]
public async Task<SampleResult?> Dynamic(string amount)
{
    var x402Result = await x402Handler.HandleX402Async(this.HttpContext,
        new PaymentRequiredInfo()
        {
            Resource = new ResourceInfoBasic
            {
                Description = "This resource is protected dynamically",
            },
            Accepts = new List<PaymentRequirementsBasic>
            {
                new PaymentRequirementsBasic
                {
                    Asset = "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
                    Amount = amount,
                    PayTo = "0x7D95514aEd9f13Aa89C8e5Ed9c29D08E8E9BfA37",
                }
            }
        },);

    if (!x402Result.CanContinueRequest)
    {
        return null; // Response already written by HandleX402Async, so just exit
    }

    //Continue with the request
}

Or use the PaymentMiddleware to require payment for a list of URLs

// Add Middleware
var paymentOptions = new PaymentMiddlewareOptions
{
    PaymentRequirements = new Dictionary<string, PaymentRequirementsConfig>()
    {
        {  "/resource/middleware", new PaymentRequirementsConfig
            {
                Version = 2,
                PaymentRequirements = new PaymentRequiredInfo
                {
                    Resource = new ResourceInfoBasic
                    {
                         MimeType = "application/json",
                        Description = "Payment Required",
                    },
                    Accepts = new()
                    {
                        new PaymentRequirementsBasic {
                            Amount = "1000",
                            Asset = "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
                            PayTo = "0x7D95514aEd9f13Aa89C8e5Ed9c29D08E8E9BfA37", // Replace with your actual wallet address
                        }
                    },
                    Discoverable = true,
                }
            }
        }
    },
};

app.UsePaymentMiddleware(paymentOptions);

Coinbase Facilitator

To use the Coinbase Facilitator, install x402.Coinbase

// Add the Coinbase Config and Facilitator
builder.Services.AddX402().WithCoinbaseFacilitator(builder.Configuration);

Add to appsettings.json:

 "CoinbaseOptions": {
   "ApiKeyId": "YOUR_COINBASE_API_KEY_ID",
   "ApiKeySecret": "YOUR_COINBASE_API_KEY_SECRET"
 }

x402 HttpClient

// Fixed private key (32 bytes hex)
var wallet = new EVMWallet("0x0123454242abcdef0123456789abcdef0123456789abcdef0123456789abcdef", chainId) //84532UL = base-sepolia
{
    IgnoreAllowances = true
};

var handler = new PaymentRequiredV2Handler(new WalletProvider(wallet));

var client = new HttpClient(handler);
var response = await client.GetAsync("https://www.x402.org/protected");

Console.WriteLine($"Final: {(int)response.StatusCode} {response.ReasonPhrase}");

See X402.Client.ConsoleSample for a complete example.

x402-dotnet Facilitator

Explore the x402.FacilitatorWeb project for a dotnet based facilitator for EVM and Solana networks.

How to test?

Follow these steps to test a x402 payment on the sample website hosted on Azure:

• Get some USDC tokens on the base-sepolia network from the Coinbase Faucet
• Use the x402 Debug Tool: https://proxy402.com/fetch
• Enter an API endpoint from the test website, for example: https://x402-dotnet.azurewebsites.net/resource/middleware
• Connect your wallet
• Click Pay
• Payment will complete and show the result: Protected by middleware

Public Facilitators

List of facilitators you can use:

• https://api.cdp.coinbase.com/platform/v2/x402/ (Coinbase, requires API key)
• https://facilitator.payai.network
• https://facilitator.mogami.tech/
• https://facilitator.daydreams.systems

View more facilitators and their status on https://www.x402dev.com

Development

There is a sample website and mock Settlement server included.

• Start the Aspire project: x402-dotnet.AppHost
• Navigate to the sample website https://localhost:7154/
• Use x402.SampleWeb.http for sample web requests

Contributions

Contributions are welcome. Fork this repository and send a pull request if you have something useful to add.

Links

Useful tools when developing x402 solutions:

• More info about x402: https://www.x402.org
• Dev tools https://x402dev.com
• Test tool https://proxy402.com/fetch
• Specifications: https://github.com/coinbase/x402/blob/main/specs/x402-specification-v2.md