I'm trying to write some middleware and need to know if the current action method (if any) has a particular filter attribute, so I can change behaviour based it's existence.
So is it possible to get a filters collection of type IList<IFilterMetadata> like you do on the ResourceExecutingContext when you are implementing an IResourceFilter?
It's not really possible today.
It is possible in ASP.NET Core 3.0
app.UseRouting();
app.Use(async (context, next) =>
{
Endpoint endpoint = context.GetEndpoint();
YourFilterAttribute filter = endpoint.Metadata.GetMetadata<YourFilterAttribute>();
if (filter != null)
{
}
await next();
});
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
RewriteContext from the response rewrite middleware.ASP.NET Core 3.0 uses a new routing which every action is an Endpoint and all attributes on the action and the controller exists on Metadata.
Here's how you can do it.
app.UseRouting();
app.Use(async (context, next) =>
{
Endpoint endpoint = context.GetEndpoint();
YourFilterAttribute filter = endpoint.Metadata.GetMetadata<YourFilterAttribute>();
if (filter != null)
{
}
await next();
});
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
Note: Not really answering directly your question, but may help depending of your needs (and the code is too long for comments)
Note 2: Not sure if it works on Core, if it doesn't, tell me and I remove the answer
You can know, in a filter, if another filter is used along with:
public class OneFilter : ActionFilterAttribute, IActionFilter
{
void IActionFilter.OnActionExecuting(ActionExecutingContext filterContext)
{
// Check if the Attribute "AnotherFilter" is used
if (filterContext.ActionDescriptor.IsDefined(typeof(AnotherFilter), true) || filterContext.Controller.GetType().IsDefined(typeof(AnotherFilter), true))
{
// things to do if the filter is used
}
}
}
public class AnotherFilter : ActionFilterAttribute, IActionFilter
{
// filter things
}
AND/OR
You can put some data in the Route data to let know the Action which Filters are used:
void IActionFilter.OnActionExecuting(ActionExecutingContext filterContext)
{
filterContext.RouteData.Values.Add("OneFilterUsed", "true");
base.OnActionExecuting(filterContext);
}
...
public ActionResult Index()
{
if(RouteData.Values["OneFilterUsed"] == "true")
{
}
return View();
}
IsDefined doesn't exist in .Net Core's ActionDescriptor.
IsDefined(), but the following can be used: if (filterContext.Filters.Any(x => filters.Contains(typeof(AnotherFilter)));) { // things to do... }