C#: What are filters in ASP.NET Core?

1public class LoggingFilter : IActionFilter
2{
3    private readonly ILogger<LoggingFilter> _logger;
4
5    public LoggingFilter(ILogger<LoggingFilter> logger)
6    {
7        _logger = logger;
8    }
9
10    public void OnActionExecuting(ActionExecutingContext context)
11    {
12        _logger.LogInformation($"Executing {context.ActionDescriptor.RouteValues["action"]}");
13    }
14
15    public void OnActionExecuted(ActionExecutedContext context)
16    {
17        _logger.LogInformation("Action completed");
18    }
19}

1[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class)]
2public class ValidateModelAttribute : ActionFilterAttribute
3{
4    public override void OnActionExecuting(ActionExecutingContext context)
5    {
6        if (!context.ModelState.IsValid)
7            context.Result = new BadRequestObjectResult(context.ModelState);
8    }
9}
10
11[HttpPost]
12[ValidateModel]
13public IActionResult Create(CreateDto dto) { }

1public class CustomExceptionFilter : IExceptionFilter
2{
3    public void OnException(ExceptionContext context)
4    {
5        context.Result = new StatusCodeResult(500);
6        context.ExceptionHandled = true;
7    }
8}