How To Configure Ing Psd2 Callback Url And Implement Marketplace Payment Splitting In Blazor Server App

I’m developing a Blazor Server web application similar to Airbnb, where hosts list properties and guests book them. The app consumes a RESTful API for backend operations. I need to implement two features:

1. Bank Account Verification for Hosts: Verify EU bank accounts (e.g., IBAN) to ensure hosts can receive payments.
2. Marketplace Checkout for Guests: Process payments from guests, splitting the amount between the host and the platform, supporting EU payment methods like iDEAL and SEPA.

What I’ve Tried

• ING Business Bank Account (PSD2 API):

  • Implemented bank verification using ING’s PSD2 API to retrieve account details.
  • Issue: The documentation requires example.com as a callback URL, which is unclear for production setup. I couldn’t find clear guidance on configuring a custom callback URL.
  • For checkout, ING Checkout relies on plugins (e.g., for WooCommerce), which are incompatible with my custom-built Blazor app.

• Tink:

  • Tested Tink for bank verification via their API.
  • Issue: The monthly subscription cost (four-digit range) is too high for my startup.

• Mollie:

  • Explored Mollie for payments.
  • Issue: Mollie supports one-to-one payments but lacks native marketplace functionality for splitting payments between hosts and the platform.

Current Implementation My app uses a clean architecture:

• Frontend: Blazor Server with Razor Pages (e.g., Profile.razor for host profile management).
• Backend: ASP.NET Core RESTful API with services like IngService.cs for PSD2 verification.
• Database: Entity Framework Core for storing host and order data.
• Existing Code: I have a working IngService.cs for PSD2 bank verification (using OAuth2 and eIDAS certificates) and a Profile.razor page where hosts enter their IBAN and bank name.

Here’s a simplified version of my current bank verification flow:

// IngService.cs (simplified)  
public class IngService : IIngService  
{  
    private readonly IHttpClientFactory _httpClientFactory;  
    private readonly IConfiguration _configuration;  
  
    public IngService(IHttpClientFactory httpClientFactory, IConfiguration configuration)  
    {  
        _httpClientFactory = httpClientFactory;  
        _configuration = configuration;  
    }  
  
    public string GetAuthorizationUrl(string redirectUri, string userId)  
    {  
        var clientId = _configuration["IngBank:ClientId"];  
        var scopes = HttpUtility.UrlEncode("payment-accounts:balances:view payment-accounts:transactions:view");  
        return $"{_configuration["IngBank:AuthBaseUrl"]}/authorize/v2/NL?client_id={clientId}&scope={scopes}&state={userId}&response_type=code&redirect_uri={HttpUtility.UrlEncode(redirectUri)}";  
    }  
  
    // Other methods for token exchange and account details  
}  

Specific Questions

• Bank Verification:

How can I configure a custom callback URL for ING’s PSD2 API in a production Blazor Server app? The example.com requirement in their documentation is confusing. Are there alternative API-based approaches to verify EU bank accounts that integrate well with Blazor Server and RESTful APIs, ideally with clear documentation and lower costs?

• Marketplace Checkout:

How can I implement payment splitting (host and platform) in a Blazor Server app using a RESTful API? For example, how do I structure the API calls and database updates to handle split payments? What’s the best way to integrate EU payment methods (e.g., iDEAL, SEPA) without relying on e-commerce platform plugins?

Requirements

• Environment: Blazor Server, .NET 8, RESTful API, Entity Framework Core.
• Region: EU (Netherlands-focused for iDEAL).
• Constraints: Must be affordable for a startup, avoid plugins designed for platforms like WooCommerce, and support marketplace payment splitting.

What I’m Looking For

• Code examples or patterns for integrating bank verification and payment splitting in Blazor Server.
• Solutions to specific issues (e.g., ING PSD2 callback URL configuration).
• Best practices for handling payment webhooks and updating order status in a database.

I’d appreciate any code snippets, configuration tips, or guidance on overcoming these challenges. Thanks!