ASP.NET MVC ActionMethodSelectorAttribute 以及HttpGet等Action特性

一、ActionMethodSelectorAttribute

　　其是一个抽象类，继承自Attribute，子类有NonActionAttribute、HttpGetAttribute、HttpPostAttribute、HttpPutAttribute、HttpDeleteAttribute、HttpPatchAttribute、HttpHeadAttribute、HttpOptionsAttribute和AcceptVerbsAttribute,其唯一抽象方法IsValidForRequest，如果返回false，结果会提示Action Not Found

[AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public abstract class ActionMethodSelectorAttribute : Attribute
{public abstract bool IsValidForRequest(ControllerContext controllerContext, MethodInfo methodInfo);
}　　

AcceptVerbsAttribute 直接继承 ActionMethodSelectorAttribute

[AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]public sealed class AcceptVerbsAttribute : ActionMethodSelectorAttribute{public AcceptVerbsAttribute(HttpVerbs verbs): this(EnumToArray(verbs)){}public AcceptVerbsAttribute(params string[] verbs){if (verbs == null || verbs.Length == 0){throw new ArgumentException(MvcResources.Common_NullOrEmpty, "verbs");}Verbs = new ReadOnlyCollection<string>(verbs);}public ICollection<string> Verbs { get; private set; }private static void AddEntryToList(HttpVerbs verbs, HttpVerbs match, List<string> verbList, string entryText){if ((verbs & match) != 0){verbList.Add(entryText);}}internal static string[] EnumToArray(HttpVerbs verbs){List<string> verbList = new List<string>();AddEntryToList(verbs, HttpVerbs.Get, verbList, "GET");AddEntryToList(verbs, HttpVerbs.Post, verbList, "POST");AddEntryToList(verbs, HttpVerbs.Put, verbList, "PUT");AddEntryToList(verbs, HttpVerbs.Delete, verbList, "DELETE");AddEntryToList(verbs, HttpVerbs.Head, verbList, "HEAD");AddEntryToList(verbs, HttpVerbs.Patch, verbList, "PATCH");AddEntryToList(verbs, HttpVerbs.Options, verbList, "OPTIONS");return verbList.ToArray();}public override bool IsValidForRequest(ControllerContext controllerContext, MethodInfo methodInfo){if (controllerContext == null){throw new ArgumentNullException("controllerContext");}string incomingVerb = controllerContext.HttpContext.Request.GetHttpMethodOverride();return Verbs.Contains(incomingVerb, StringComparer.OrdinalIgnoreCase);}}

　　除了NonActionAttribute，内部都是通过AcceptVerbsAttribute 来实现的，如HttpGetAttribute,其他都类似

  [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]public sealed class HttpGetAttribute : ActionMethodSelectorAttribute{private static readonly AcceptVerbsAttribute _innerAttribute = new AcceptVerbsAttribute(HttpVerbs.Get);public override bool IsValidForRequest(ControllerContext controllerContext, MethodInfo methodInfo){return _innerAttribute.IsValidForRequest(controllerContext, methodInfo);}}

　　NonActionAttribute，IsValidForRequest直接返回false

 [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]public sealed class NonActionAttribute : ActionMethodSelectorAttribute{public override bool IsValidForRequest(ControllerContext controllerContext, MethodInfo methodInfo){return false;}}

二、ActionNameSelectorAttribute

　　其是一个抽象类，继承自Attribute，子类有ActionNameAttribute

 [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]public abstract class ActionNameSelectorAttribute : Attribute{public abstract bool IsValidName(ControllerContext controllerContext, string actionName, MethodInfo methodInfo);}

    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]public sealed class ActionNameAttribute : ActionNameSelectorAttribute{public ActionNameAttribute(string name){if (String.IsNullOrEmpty(name)){throw new ArgumentException(MvcResources.Common_NullOrEmpty, "name");}Name = name;}public string Name { get; private set; }public override bool IsValidName(ControllerContext controllerContext, string actionName, MethodInfo methodInfo){
　　　　　　　//只是验证根据请求进行路由匹配出的actionName，是否和ActionName特性上指定的Name相等return String.Equals(actionName, Name, StringComparison.OrdinalIgnoreCase);}}

三、自定义ActionMethodSelectorAttribute

　　验证请求是GET而且是ajax的

 public class MyActionMethodSelectorAttribute : ActionMethodSelectorAttribute{public override bool IsValidForRequest(ControllerContext controllerContext, System.Reflection.MethodInfo methodInfo){//get/poststring httpMethodOverride = controllerContext.HttpContext.Request.GetHttpMethodOverride();//isAjaxvar isAjax = controllerContext.HttpContext.Request.IsAjaxRequest();var b = httpMethodOverride.ToLower() == "get" && isAjax;return b;}}