How to Access Services in a Custom Attribute That Extends Attribute and Implements IAuthorizationFilter in .Net 8

To access services in your custom attribute that implements IAuthorizationFilter and extends Attribute in a .NET Core application, you can follow these steps:

1. Implement the Custom Attribute: Create a custom authorization filter attribute by extending Attribute and implementing IAuthorizationFilter.

2. Get Services from HttpContext: Use the HttpContext to obtain the required services. The HttpContext provides an HttpContext.RequestServices property, which is an IServiceProvider and you can use it to get the required service.

Here is a simplified example:

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.Extensions.DependencyInjection;
using System;

public class CustomAuthorizationAttribute : Attribute, IAuthorizationFilter
{
    public void OnAuthorization(AuthorizationFilterContext context)
    {
        // Get services from HttpContext
        var myService = context.HttpContext.RequestServices.GetService<IMyService>();

        // Use your service here
        if (myService != null)
        {
            // Perform custom authorization logic using myService
            if (!myService.IsAuthorized(context.HttpContext.User))
            {
                context.Result = new ForbidResult();
            }
        }
        else
        {
            context.Result = new ForbidResult();
        }
    }
}

// Your service interface
public interface IMyService
{
    bool IsAuthorized(System.Security.Claims.ClaimsPrincipal user);
}

// Your service implementation
public class MyService : IMyService
{
    public bool IsAuthorized(System.Security.Claims.ClaimsPrincipal user)
    {
        // Your authorization logic
        return user.Identity.IsAuthenticated;
    }
}

3. Register Your Service in the DI Container: In your Program.cs or Startup.cs file, register your service with the dependency injection container.

// In Program.cs for .NET 6 or later
var builder = WebApplication.CreateBuilder(args);

builder.Services.AddScoped<IMyService, MyService>();

var app = builder.Build();

// Continue app setup...

app.Run();

4. Use Your Custom Authorization Attribute: Apply your custom attribute to controllers or actions as needed.

[CustomAuthorization]
public class MyController : ControllerBase
{
    // Your controller actions here
}

This structure allows you to leverage dependency injection within your custom attribute, enabling you to use various services that are part of your application’s service collection.

Remember to handle null checks and exceptions appropriately to ensure the robustness of your authorization logic.