using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;

namespace DotNet6CustomAttribute.Attributes
{
    public class HeaderCheckAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(ActionExecutingContext context)
        {
            // Get all headers
            var headers = context.HttpContext.Request.Headers;

            // Check if headers has x-dotnet-6-custom-attribute
            if (!headers.ContainsKey("x-dotnet-6-custom-attribute"))
            {
                context.Result = new BadRequestObjectResult("The header x-dotnet-6-custom-attribute is missing");
            }
            else if (string.IsNullOrEmpty(headers["x-dotnet-6-custom-attribute"]))
            {
                context.Result = new BadRequestObjectResult("The header x-dotnet-6-custom-attribute can't be null or empty");
            }

            base.OnActionExecuting(context);
        }
    }
}

using DotNet6CustomAttribute.Attributes;
using Microsoft.AspNetCore.Mvc;

namespace DotNet6CustomAttribute.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class WeatherForecastController : ControllerBase
    {
        private static readonly string[] Summaries = new[]
        {
        "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
    };

        private readonly ILogger<WeatherForecastController> _logger;

        public WeatherForecastController(ILogger<WeatherForecastController> logger)
        {
            _logger = logger;
        }

        [HttpGet]
        [Route("GetWeatherForecastWithCheck")]
        [HeaderCheckAttribute]
        public IEnumerable<WeatherForecast> GetWithCheck()
        {
            return Enumerable.Range(1, 5).Select(index => new WeatherForecast
            {
                Date = DateTime.Now.AddDays(index),
                TemperatureC = Random.Shared.Next(-20, 55),
                Summary = Summaries[Random.Shared.Next(Summaries.Length)]
            })
            .ToArray();
        }

        [HttpGet]
        [Route("GetWeatherForecastWithoutCheck")]
        public IEnumerable<WeatherForecast> GetWithoutCheck()
        {
            return Enumerable.Range(1, 5).Select(index => new WeatherForecast
            {
                Date = DateTime.Now.AddDays(index),
                TemperatureC = Random.Shared.Next(-20, 55),
                Summary = Summaries[Random.Shared.Next(Summaries.Length)]
            })
            .ToArray();
        }
    }
}