Custom Exception Middleware

It is a middleware for error handling in ASP.NET projects, the application aims to facilitate and handle when an accidental or custom exception occurs in the project.

Install

• Package Manager Console

Install-Package CustomExceptionMiddleware

• .Net CLI

dotnet add package CustomExceptionMiddleware

Minimum requirements to use: .NET Standard 2.0

Compilation requirements: .NET 8

How to use

It's very simple to use, go to Startup.cs on Configure() method and add this code:

app.UseCustomExceptionMiddleware();

Or if you are using any of the newer versions of .NET put the code after the app build on Program.cs file.

var app = builder.Build();
app.UseCustomExceptionMiddleware();

Example output

{
    "type": "VALIDATION_ERRORS",
    "error": {
        "msg": "Custom domain exception message"
    }
}

Custom use

• Create object options
  It's possible create a CustomExceptionOptions to customize the return middleware object, to view the StackTrace like this:

  app.UseCustomExceptionMiddleware(new CustomExceptionOptions
  {
      ViewStackTrace = true
  });

• Use an action options
  Other options to customize the return object is using an action to create a CustomErrorModel

  app.UseCustomExceptionMiddleware(options =>
  {
      options.ViewStackTrace = true;
  });

In both cases the output will include de stack trace in detail object property:

Example output

{
    "type": "VALIDATION_ERRORS",
    "error": {
        "msg": "Custom domain exception message",
        "detail": "at CustomExceptionMiddleware.WebAppTest.Custom.ProductService.GetDomainException(Boolean returnProducts) in C:\\isaacnborges\\projects\\custom-exception-middleware\\tests\\CustomExceptionMiddleware.WebAppTest.Custom\\ProductService.cs:line 18\r\n   at CustomExceptionMiddleware.WebAppTest.Custom.Controllers.ProductController.GetDomain(Boolean returnProduct) in C:\\isaacnborges\\projects\\custom-exception-middleware\\tests\\CustomExceptionMiddleware.WebAppTest.Custom\\Controllers\\ProductController.cs:line 26"
    }
}

Configure Exceptions

This middleware use some custom exceptions to catch and personalize the response status code.

The custom middleware supports the following Exceptions:

Exception	Status code description	Status code
DomainException	BadRequest	400
UnauthorizedException	Unauthorized	401
CannotAccessException	Forbidden	403
NotFoundException	NotFound	404
Exception	InternalServerError	500

DomainException is an abstract exception, so to use it's necessary create other exception and inherit. The others exceptions only throw an exception

Custom exception example

public class InvalidStateException : DomainException
{
        public InvalidStateException()
        { }

        public InvalidStateException(string message) : base(message)
        { }

        public InvalidStateException(string message, Exception innerException) : base(message, innerException)
        { }
}

Throw exceptions

throw new InvalidStateException("Custom domain exception message");
throw new UnauthorizedException("Custom unauthorized exception message");
throw new CannotAccessException("Custom cannot access exception message");
throw new NotFoundException("Custom not found exception message");
throw new Exception("Custom exception message");

Customize exception type

It's possible to customize the exception type when throw an exception, just pass the type in an exception constructor.

throw new CustomDomainException("Custom domain exception message", "OTHER_CUSTOM_TYPE");

Samples

Inside the samples folder has two projects that could be used for test the and validate the middleware.

Run the sample projects

• WebAppTest

  dotnet run --project .\samples\CustomExceptionMiddleware.WebAppTest\
  

• WebAppTest.Custom

  dotnet run --project .\samples\CustomExceptionMiddleware.WebAppTest.Custom\
  

Samples documentation

• Swagger
  • WebAppTest
  • WebAppTest.Custom
• Postman
  • Open docs folder, inside has a postman collection that could be used for test.

Logging

This middleware will Log some informations that can be used for monitoring and observability, like TraceIdentifier, request and exception informations like message type and stack trace:

Example log:

Occurred an exception - TraceId: 0HMBO9LGH0JHD:00000002 - ExceptionType: InvalidStateException - Message: Custom domain exception message
CustomExceptionMiddleware.WebAppTest.InvalidStateException: Custom domain exception message
at CustomExceptionMiddleware.WebAppTest.Custom.ProductService.GetDomainException(Boolean returnProducts) in C:\\isaacnborges\\projects\\custom-exception-middleware\\tests\\CustomExceptionMiddleware.WebAppTest.Custom\\ProductService.cs:line 18\r\n   at CustomExceptionMiddleware.WebAppTest.Custom.Controllers.ProductController.GetDomain(Boolean returnProduct) in C:\\isaacnborges\\projects\\custom-exception-middleware\\tests\\CustomExceptionMiddleware.WebAppTest.Custom\\Controllers\\ProductController.cs:line 26

Using custom attribute

In some scenarios the project needs other response object, integrations with 3rd party systems for example, this middleware contains an attribute that could be ignore, it's possible use in class or methods

Using the IgnoreCustomExceptionAttribute attribute the middleware will ignore your own flow. To use it simply, decorate the class or method with the name.

• Class example

  [IgnoreCustomException]
  public class ValuesController : ControllerBase
  {
      [HttpGet]
      public IActionResult Get()
      {
          throw new CustomDomainException("Some error ignore class");
      }

• Method example

  [IgnoreCustomException]
  [HttpGet("ignore")]
  public IActionResult GetIgnore()
  {
      throw new CustomDomainException("Some error ignore method");
  }

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License

MIT