asp.net - Creating an action filter attribute that bypasses the actual execution of the action and returns a value for it

Question

Can I create an ActionFilterAttribute that bypasses the actual execution of the action and returns a value for it?

Answer 1

对的，这是可能的。您可以设置在覆盖时提供给您的过滤器上下文的OnActionExecuting结果ActionFilterAttribute。

using System.Web.Mvc;

public sealed class SampleFilterAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting( ActionExecutingContext filterContext )
    {
        filterContext.Result = new RedirectResult( "http://google.com" );
    }
}

在源代码中，您可以看到设置Result过滤器上下文的属性会更改流程。

来自 System.Web.Mvc.ControllerActionInvoker：

internal static ActionExecutedContext InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func<ActionExecutedContext> continuation)
{
    filter.OnActionExecuting(preContext);
    if (preContext.Result != null)
    {
        return new ActionExecutedContext(preContext, preContext.ActionDescriptor, true /* canceled */, null /* exception */)
        {
            Result = preContext.Result
        };
    }

    // other code ommitted
}

Answer 2

你可以像这样：

1）重定向到一些动作，然后返回一些值：

public class MyFilterAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        /*If something happens*/
        if (/*Condition*/)
        {
            /*You can use Redirect or RedirectToRoute*/
            filterContext.HttpContext.Response.Redirect("Redirecto to somewhere");
        }

        base.OnActionExecuting(filterContext);
    }
 }

2）将一些值直接写入请求并结束它发送给客户端：

public class MyFilterAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        /*If something happens*/
        if (/*Condition*/)
        {
            filterContext.HttpContext.Response.Write("some value here");
            filterContext.HttpContext.Response.End();
        }

        base.OnActionExecuting(filterContext);
    }
 }