filters.Add vs FilterProviders.Providers.Add

问题:

I came across a sample MVC3 code which had following in the Global.asax file:

public static void RegisterGlobalFilters(....)
{
    filters.Add(new MyFilter1());
    ....
    var provider = new MyFilterProvider();
    provider.Add(c => c.HttpContext.IsDebuggingEnabled ? new MyProvider2() : null);
    FilterProviders.Providers.Add(provider)
}

Both MyProvider1 and MyProvider2 are implemented with IResultFilter, and I am confused why one of them is added to FilterProviders and the other one is registered as a global filter.

Why and when should we add custom filters on FilterProvider, and why and when should we register them as global filters?

回答1:

When you add a filter to GlobalFilters.Filters the filter will get executed for every request.

When you add an IFilterProvider to FilterProviders.Providers the filter provider will have a chance to decide whether a particular filter applies to the current request.

FilterProviders gives you greater control while GlobalFilters makes it easy to register a filter for the entire site.