c# – 如何在ActionExecutingContext中访问ActionDescriptor的Me

我的应用程序上有一个ActionFilterAttribute,用于在检测到用户未经过身份验证时重定向用户.在过滤器中,我想检测一个动作的ReturnType何时是JsonResult.

作为一种解决方法,我最初创建了IsJsonResult的自定义属性,并使用该属性修饰了我的解决方案中的JsonResult方法.这有效,并在动作过滤器中实现如下：

public class CheckUser : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext actionExecutingContext)
    {
        base.OnActionExecuting(actionExecutingContext);
        object[] customAttributes = actionExecutingContext.ActionDescriptor.GetCustomAttributes(true);
        bool isJsonResult = customAttributes.FirstOrDefault(a => a.GetType() == typeof(IsJsonResult)) != null;

        if (isJsonResult)
        {
            return; // Don't perform any additional checks on JsonResult requests.
        }

        // Additional checking code omitted.
    }
}

这有效,但我不喜欢在这个项目中装饰所有JsonResult动作的想法.如果将新的JsonResult添加到项目中,那很容易失败,我们忘记相应地装饰它.

此外,我可以看到名为“JsonResult”的ReturnType位于上面显示的actionExecutingContext对象中的调试器中.以下是观察窗口中显示的路径：

actionExecutingContext > ActionDescriptor > [System.Web.Mvc.ReflectedActionDescriptor] > MethodInfo > ReturnType > FullName

该FullName属性的值为“System.Web.Mvc.JsonResult”.

所以我似乎可以直接从actionExecutingContext对象中提取该值,并创建一个支持方法来返回一个bool指标.为此,这里是我编写的代码.

private bool isReturnTypeJson(ActionExecutingContext actionExecutingContext)
    {
        string actionName = actionExecutingContext.ActionDescriptor.ActionName;
        string controllerName = actionExecutingContext.ActionDescriptor.ControllerDescriptor.ControllerName;
        Type controllerType = actionExecutingContext.Controller.GetType();
        try
        {
            // Only effective when the actionName is not duplicated in the controller.
            Type returnType = controllerType.GetMethod(actionName).ReturnType;
            return (returnType.Name == "JsonResult");
        }
        catch (AmbiguousMatchException)
        {
            // Using LINQ,can I filter this collection to isolate just the methods
            // that have the same name as the "actionName" variable above?
            MethodInfo[] methodsInfoCollection = controllerType.GetMethods(BindingFlags.Public | BindingFlags.Instance);

            // Attempted code from https://stackoverflow.com/questions/15283158/net-mvc-counting-action-methods-in-web-application
            //var info = typeof(controllerType)
            //        .Assembly.GetTypes()
            //        .Where(t => typeof(Controller).IsAssignableFrom(t))
            //        .Where(t => t.Namespace.StartsWith("AwesomeProduct.Web"))
            //        .SelectMany(t => t.GetMethods(BindingFlags.Public | BindingFlags.Instance))
            //        .Where(m => typeof(ActionResult).IsAssignableFrom(m.ReturnType))
            //        .Where(m => !m.IsAbstract)
            //        .Where(m => m.GetCustomAttribute<NonActionAttribute>() == null);

        }
        return false;
    }

只要控制器中的操作名称是唯一的,分配returnType就可以在try-block中运行.但是如果控制器中有多个相同操作名称的实例,则会发生AmbiguousMatchException.所以在catch-block中,我已经将方法分配给了一个集合.使用LINQ,如何将methodsInfoCollection变量中的值过滤到通过ActionExecutingContext到达的操作？

我研究过的一些文章如下,并使用了一些这些文章.但我还没想到这一点.

> http://www.codeproject.com/Articles/742461/Csharp-Using-Reflection-and-Custom-Attributes-to-M
> Can I get an Action’s return type from an Action Filter?
> .NET MVC: Counting Action methods in web application

谢谢你的帮助.

==============

更新为原始代码.这样可行,但循环并不理想.

private bool isReturnTypeJson(ActionExecutingContext actionExecutingContext)
{
    string actionName = actionExecutingContext.ActionDescriptor.ActionName;
    string controllerName = actionExecutingContext.ActionDescriptor.ControllerDescriptor.ControllerName;
    Type controllerType = actionExecutingContext.Controller.GetType();
    try
    {
        // Only effective when the actionName is not duplicated in the controller.
        Type returnType = controllerType.GetMethod(actionName).ReturnType;
        return (returnType.Name == "JsonResult");
    }
    catch (AmbiguousMatchException)
    {
        // Using LINQ,can I filter this collection to isolate just the methods with a name of actionName.
        MethodInfo[] methodInfoCollection = controllerType.GetMethods(BindingFlags.Public | BindingFlags.Instance);
        foreach (MethodInfo methodInfo in methodInfoCollection)
        {
            if (methodInfo.ReturnType != null) {
                if (methodInfo.ReturnType == typeof(ActionResult))
                {
                    return false;
                }
                if (methodInfo.ReturnType == typeof(JsonResult))
                {
                    return true;
                }
            }
        }
    }
    return false;
}

请参阅下面的Reza Aghaei的解决方案.他的解决方案完全消除了对单独方法的需求.

((ReflectedActionDescriptor)filterContext.ActionDescriptor).MethodInfo.ReturnType

((ReflectedActionDescriptor)filterContext.ActionDescriptor).MethodInfo.ReturnType == typeof(JsonResult)

public JsonResult Index()
{
    return Json(new { });
}