在.NET Core MVC中，如何在AuthorizationHandler中访问DbContext？

Question

Here is my startup code to configure services:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    services.AddDbContext<ThisApplicationDbContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

    services.AddAuthentication(
        SharedOptions => SharedOptions.SignInScheme = CookieAuthenticationDefaults.AuthenticationScheme);

    services.AddAuthorization(
         options => { options.AddPolicy("ValidUsers",
             policy =>
             {
                policy.Requirements.Add(new ValidUserAuthorization());
             });
         });
}

And here is the class for authorizing users:

public class ValidUserAuthorization : AuthorizationHandler<ValidUserAuthorization>, IAuthorizationRequirement
{
    protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, ValidUserAuthorization requirement)
    {
        string username = context.User.Identity.Name;

        if (context.User.Identity.Name == "hardcoded-username")
        {
            context.Succeed(requirement);
        }
        return Task.CompletedTask;
    }
}

I would like to change my authorization class ( ValidUserAuthorization ) to be able to look up the username in my application database (as accessed via ThisApplicationDbContext ), rather than comparing against hard-coded strings.

What is the best way of obtaining this database context (as already initialized in ConfigureServices ) and having the authorization class use it?

Answer 1

One possible way of doing it is by passing the type of your DbContext as a generic type:

public class ValidUserAuthorization<TDbContext> : AuthorizationHandler<ValidUserAuthorization>, IAuthorizationRequirement
    where TDbContext : DbContext, new()
{
    protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, ValidUserAuthorization requirement)
    {
        using (TDbContext db = new TDbContext())
        {
            // ...
        }
    }
}

Then you can create the ValidUserAuthorization object like this in your ConfigureServices method:

policy.Requirements.Add(new ValidUserAuthorization<ThisApplicationDbContext>());