ErrorResultResponse

Namespace: RA.Utilities.Api.Mapper

The ErrorResultResponse is a static helper class that provides a clean, centralized way to map exceptions from the RA.Utilities.Core layer into standardized IResult objects for ASP.NET Core Minimal APIs. It is a key component for creating consistent error responses when using the Result<T> pattern.

🎯 Purpose

When your application logic returns a Result<T> that is in a Failure state, it contains an Exception object (e.g., NotFoundException, ConflictException). The ErrorResultResponse.Result method inspects this exception and automatically generates the appropriate HTTP error response (404 Not Found, 409 Conflict, etc.) using the standardized models from RA.Utilities.Api.Results.

This allows you to handle all expected business-level failures in a single, declarative line of code within your API endpoints, keeping them clean and free of repetitive error-handling logic.

🚀 How to Use

The primary use case for ErrorResultResponse is within the Match method of a Result<T> object. The ErrorResultResponse.Result method has the signature Func<Exception, IResult>, which perfectly matches the signature required by the failure delegate of Match.

This allows you to pass the method directly, creating highly readable and maintainable endpoint code.

Example

Imagine you have a service that retrieves a product and returns a Result<Product>. The result will be a Failure containing a NotFoundException if the product doesn't exist.

In your Minimal API endpoint, you can use ErrorResultResponse.Result to handle this failure case automatically.

1. The Service Layer returning a Result

// Application/Features/Products/ProductService.cs
using RA.Utilities.Core;
using RA.Utilities.Core.Exceptions;

public class ProductService
{
    public Result<Product> GetProductById(int id)
    {
        // Simulate not finding a product
        if (id != 1)
        {
            // Return a failure Result containing a NotFoundException
            return new NotFoundException(nameof(Product), id);
        }

        // Return a success Result with the product
        return new Product { Id = id, Name = "Sample Product" };
    }
}

2. The API Endpoint using Match and ErrorResultResponse

using RA.Utilities.Api.Mapper

// Api/Features/Products/ProductEndpoints.cs
app.MapGet("/products/{id}", (int id, ProductService service) => 
{
    Result<Product> result = service.GetProductById(id);
    
    // The Match method handles both success and failure outcomes.
    // The `ErrorResultResponse.Result` method is passed directly to the failure delegate.
    return result.Match<IResult>(
        success: product => SuccessResponse.Ok(product),
        failure: ErrorResultResponse.Result 
    );
});

What Happens

• If you request /products/1, the result is a success, and the success delegate is executed, returning a 200 OK with the product data.
• If you request /products/99, the result is a failure containing a NotFoundException. The failure delegate (ErrorResultResponse.Result) is executed. It inspects the exception, sees it's a NotFoundException, and automatically returns a 404 Not Found with a standardized JSON body:

{
  "responseCode": 404,
  "responseType": "NotFound",
  "responseMessage": "Product with value '99' not found.",
  "result": {
    "entityName": "Product",
    "entityValue": 99
  }
}