Exception Handling in .net core

 Global Middleware for Exception

• Use custom middleware to catch and handle unhandled exceptions

• Register middleware early in the pipeline (before routing)

• Log exceptions and return a consistent error response (e.g., ProblemDetails format)

Example:

public class GlobalExceptionMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger<GlobalExceptionMiddleware> _logger;

    public GlobalExceptionMiddleware(RequestDelegate next, ILogger<GlobalExceptionMiddleware> logger)
    {
        _next = next;
        _logger = logger;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await _next(context); // Proceed to next middleware
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Unhandled exception occurred.");
            context.Response.StatusCode = 500;
            context.Response.ContentType = "application/json";

            var response = new { error = ex.Message, trace = ex.StackTrace };
            await context.Response.WriteAsJsonAsync(response);
        }
    }
} 

Register in Program.cs:

app.UseMiddleware<GlobalExceptionMiddleware>();

1. What are the ways to handle exceptions in .NET Core?Try-Catch blocks in service or controller methods

• Exception filters (IExceptionFilter, ExceptionFilterAttribute) in MVC
• Global exception handling via custom middleware
• UseStatusCodePages for simple status code mapping
• Use of ProblemDetails object for standard error responses

2. What’s the difference between middleware-based exception handling and exception filters?



Best Practice: Use middleware for global error handling and filters for controller-specific scenarios.

Write sample custom exception.

public class UserNotFoundException : Exception

{
    public UserNotFoundException(int userId)
        : base($"User with ID {userId} was not found.") { }
}