What are Global Exception Filters in ASP.NET Core?

Global Exception Filters in ASP.NET Core provide a centralized mechanism for handling unhandled exceptions generated during MVC controller or Razor Pages execution.

Instead of writing repetitive try-catch blocks throughout individual controller actions, an exception filter can provide a consistent mechanism for logging exceptions, transforming errors into appropriate responses, and applying application-specific error-handling behavior.

However, there is an important architectural consideration: Microsoft recommends using exception-handling middleware such as UseExceptionHandler for general application-wide exception handling, because middleware is more flexible than exception filters. Exception filters are particularly useful when the error-handling behavior needs to differ depending on the MVC action or controller.

Why Use Exception Filters?

Consider an application containing hundreds of controller actions.

Without centralized exception handling, developers might write:

try
{
    // business operation
}
catch(Exception ex)
{
    // log exception
    // return error response
}

repeatedly.

This creates:

• Code duplication
• Inconsistent error responses
• Difficult maintenance
• Inconsistent logging
• Higher risk of exposing internal exception information

A global exception filter can centralize this behavior for MVC-based applications.

How Does an Exception Filter Work?

The conceptual flow is:

HTTP Request → Controller → Action → Exception → Exception Filter → Error Response

An exception filter can inspect the exception and determine the appropriate response.

For example:

• ValidationException → HTTP 400
• UnauthorizedAccessException → HTTP 401/403
• Business exception → appropriate application response
• Unexpected exception → HTTP 500

The filter can set ExceptionHandled or assign a Result, which stops exception propagation through the MVC pipeline.

Global Exception Filter vs Exception Middleware

This distinction is important for experienced ASP.NET Core developers.

Exception Filter

Best suited for:

• MVC-specific exception handling
• Controller/action-specific behavior
• Different error formats for particular MVC scenarios
• View-specific error handling

Exception Middleware

Better suited for:

• Global application-level exception handling
• APIs and web applications
• Consistent error responses
• Centralized logging
• Correlation IDs
• Problem Details responses
• Cross-cutting error-handling requirements

Microsoft recommends UseExceptionHandler unless the application's requirements specifically call for action-dependent exception handling.

Enterprise Best Practice

A production ASP.NET Core API should generally implement a centralized error-handling strategy that:

1. Logs the exception securely.
2. Generates a correlation/trace identifier.
3. Returns a consistent error contract.
4. Avoids exposing stack traces to clients.
5. Maps known exceptions to appropriate HTTP status codes.
6. Uses structured logging and monitoring.
7. Separates developer diagnostics from production error responses.

For modern APIs, Problem Details is commonly used as a standardized representation for HTTP API errors.

Key takeaway: Global exception filters are valuable, but they should not automatically be treated as the default solution for every ASP.NET Core application. The correct choice depends on whether exception handling needs to be MVC/action-specific or application-wide.