Override Authorize Attribute in ASP.NET MVC

Edit: Since ASP.NET MVC 4 the best approach is simply to use the built-in AllowAnonymous attribute.

The answer below refers to earlier versions of ASP.NET MVC

You could create a custom authorisation attribute inheriting from the standard AuthorizeAttribute with an optional bool parameter to specify whether authorisation is required or not.

public class OptionalAuthorizeAttribute : AuthorizeAttribute
{
    private readonly bool _authorize;

    public OptionalAuthorizeAttribute()
    {
        _authorize = true;
    }

    public OptionalAuthorizeAttribute(bool authorize)
    {
        _authorize = authorize;
    }

    protected override bool AuthorizeCore(HttpContextBase httpContext)
    {
        if(!_authorize)
            return true;

                    return base.AuthorizeCore(httpContext);
    }
}

Then you can decorate your base controller with that attribute:

[OptionalAuthorize]
public class ControllerBase : Controller
{
}

and for any controllers you don’t want authorisation simply use the override with a ‘false’ – e.g.

[OptionalAuthorize(false)]
public class TestController : ControllerBase
{
    public ActionResult Index()
    {
        return View();
    }
}