Exception Handling in ASP.NET Core - Complete Guide

Exception handling is a critical part of building secure and reliable ASP.NET Core applications.
If exceptions are not handled properly, they can expose sensitive information, crash APIs, or make debugging extremely difficult.

ASP.NET Core provides two powerful mechanisms for handling exceptions globally:

Exception Handling Middleware
Exception Filters

In this article, you will learn:

How exception handling works in ASP.NET Core
Middleware vs Filters differences
When to use Middleware, Filters, or both
Best practices followed in real-world production applications

Why Exception Handling Is Important in ASP.NET Core

Poor exception handling can cause:

Application crashes ❌
Exposed stack traces ❌
Inconsistent API responses ❌
Difficult debugging ❌

Proper exception handling ensures:

Centralized error handling ✅
Secure API responses ✅
Clean and maintainable code ✅
Better logging and monitoring ✅

What Is Exception Handling Middleware in ASP.NET Core?

Exception handling middleware sits early in the ASP.NET Core request pipeline.
It can catch any unhandled exception, regardless of where it occurs.

What Can Middleware Handle?

Controller exceptions
Service and repository exceptions
Database failures
Runtime errors
Filter exceptions

Global Exception Handling Middleware Example

public class ExceptionMiddleware
{
    private readonly RequestDelegate _next;

    public ExceptionMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        {
            context.Response.StatusCode = StatusCodes.Status500InternalServerError;
            context.Response.ContentType = "application/json";

            var response = new
            {
                message = "Something went wrong",
                error = ex.Message
            };

            await context.Response.WriteAsJsonAsync(response);
        }
    }
}

Register Middleware in Program.cs

app.UseMiddleware<ExceptionMiddleware>();

Advantages of Exception Handling Middleware

✅ Catches all unhandled exceptions
✅ Ideal for REST APIs
✅ Perfect for logging and monitoring
✅ Provides consistent error responses

Limitations of Middleware

❌ No access to ModelState
❌ No controller or action context
❌ Cannot handle MVC-specific validation errors

What Are Exception Filters in ASP.NET Core?

Exception Filters are part of the MVC execution pipeline.
They execute only when an exception occurs inside a controller action.

What Filters Can Access?

Controller and action context
ModelState
Action arguments

Custom Exception Filter Example

public class GlobalExceptionFilter : IExceptionFilter
{
    public void OnException(ExceptionContext context)
    {
        context.Result = new ObjectResult(new
        {
            message = "Controller error occurred",
            details = context.Exception.Message
        })
        {
            StatusCode = StatusCodes.Status500InternalServerError
        };

        context.ExceptionHandled = true;
    }
}

Register Filter Globally

services.AddControllers(options =>
{
    options.Filters.Add<GlobalExceptionFilter>();
});

Advantages of Exception Filters

✅ Access to MVC context
✅ Ideal for validation & business exceptions
✅ Controller-specific error handling

Limitations of Exception Filters

❌ Cannot catch middleware or routing errors
❌ Only works inside MVC
❌ Not suitable for global logging alone

Middleware vs Filters – Key Differences

Feature	Middleware	Filters
Pipeline Scope	Entire App	MVC Only
Catches All Exceptions	✅ Yes	❌ No
Access to ModelState	❌ No	✅ Yes
Best for APIs	✅ Yes	⚠ Limited
Logging & Monitoring	✅ Excellent	❌ Limited

Which One Should You Use?

✔ Use Middleware When:

Building REST APIs
Handling global exceptions
Implementing centralized logging
Returning consistent error responses

✔ Use Filters When:

Handling validation errors
Customizing controller responses
Managing action-level exceptions

Best Practice – Use Middleware and Filters Together

🔹 Middleware → Global exception handling & logging
🔹 Filters → MVC-specific and validation errors

This layered approach is used in enterprise-grade ASP.NET Core applications.

Exception Handling Flow in ASP.NET Core

ASP.NET Core MVC and Razor Pages filter pipeline showing resource filters, model binding, validation, action and exception filters execution order

ASP.NET Core Middleware Request Pipeline Execution Order

HTTP Request
   ↓
Exception Handling Middleware
   ↓
Routing
   ↓
Authorization
   ↓
Exception Filters
   ↓
Controller Action
   ↓
HTTP Response

Common Interview Question

Q: Should we use Exception Middleware or Filters?
✔ Use Middleware for global handling
✔ Use Filters for MVC-specific handling
✔ Best solution → Use both

Conclusion

Exception handling is not optional—it’s a core architectural requirement in ASP.NET Core.

📌 Summary

Middleware handles global exceptions
Filters handle MVC-specific exceptions
Using both ensures secure, clean, and scalable applications

Read our detailed guides on Request Pipeline – Complete Execution & Middleware vs Filters in detail.

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Exception Handling in ASP.NET Core – Complete Guide