ActionFilterAttribute Class

Typically, you create an action or response filter by creating an attribute class that inherits from the abstract ActionFilterAttribute class. Some built-in action filters, such as AuthorizeAttribute and HandleErrorAttribute, inherit from the FilterAttribute class. Other action filters, such as OutputCacheAttribute, inherit from the abstract ActionFilterAttribute class, which enables the action filter to run either before or after the action method runs.

You can use filter attributes to mark any action method or controller. If the attribute marks a controller, the filter applies to all action methods in that controller.

For more information about using attributes, see Extending Metadata Using Attributes.

The following example shows how to create a simple action filter that logs trace messages before and after an action method is called.

public class LoggingFilterAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        filterContext.HttpContext.Trace.Write("(Logging Filter)Action Executing: " +
            filterContext.ActionDescriptor.ActionName);

        base.OnActionExecuting(filterContext);
    }

    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        if (filterContext.Exception != null)
            filterContext.HttpContext.Trace.Write("(Logging Filter)Exception thrown");

        base.OnActionExecuted(filterContext);
    }
}

Reference

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