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What is the purpose of global exception handling middleware in an ASP.NET Core application? What happens by default in ASP.NET Core if you don't configure any global exception handling middleware at all? How do you map different exception types to different HTTP status codes in a global exception handler? How do you handle exceptions specifically within minimal API endpoints, given they don't use the traditional MVC exception filter pipeline? What is the difference between handling exceptions with middleware versus using try/catch blocks directly in controller actions? How should a global exception handler differentiate between exceptions that should return specific client-facing details versus exceptions that should always show a generic message? What is the role of the [ApiController] attribute in automatically handling certain error scenarios without explicit exception handling code? How do you write an integration test verifying that your global exception handler produces the correct error response shape? What is ProblemDetails (RFC 7807/9457), and how does ASP.NET Core support it for standardized error responses? What information should be excluded from error responses in production to avoid leaking sensitive implementation details?
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How does the IExceptionHandler interface (introduced in .NET 8) provide a more structured alternative to the UseExceptionHandler lambda approach?

Intermediate

Answer

IExceptionHandler defines a TryHandleAsync(HttpContext, Exception, CancellationToken) method that you implement as a proper, testable, DI-injectable class rather than an inline delegate -- multiple exception handlers can be registered and are tried in order until one returns true (indicating it handled the exception), enabling different handlers for different exception types (like a specific handler for validation exceptions and a fallback handler for everything else) in a clean, composable way.
public class ValidationExceptionHandler : IExceptionHandler {
    public async ValueTask<bool> TryHandleAsync(HttpContext context, Exception exception, CancellationToken ct) {
        if (exception is not ValidationException ve) return false;  // not handled, try next handler
        context.Response.StatusCode = 400;
        await context.Response.WriteAsJsonAsync(new { errors = ve.Errors }, ct);
        return true;
    }
}

builder.Services.AddExceptionHandler<ValidationExceptionHandler>();
builder.Services.AddExceptionHandler<GlobalExceptionHandler>();  // fallback
Real-world example An API registers a specific ValidationExceptionHandler that formats validation errors distinctly, chained with a catch-all GlobalExceptionHandler for everything else, replacing what used to be a large if/else chain inside a single exception-handling lambda.

Common follow-ups: What determines the order multiple registered IExceptionHandlers are tried in?;How does this integrate with ProblemDetails for standardized error responses?

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All 15 Global Exception Handling & Middleware questions