ActionFilterAttribute Class

Článek
02/21/2011

Represents the base class for all action-filter attributes.

Inheritance Hierarchy

System.Object
  System.Attribute
    System.Web.Mvc.FilterAttribute
      System.Web.Mvc.ActionFilterAttribute
        System.Web.Mvc.AsyncTimeoutAttribute
        System.Web.Mvc.OutputCacheAttribute

Namespace: System.Web.Mvc
Assembly: System.Web.Mvc (in System.Web.Mvc.dll)

Syntax

'Declaration
<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Method, Inherited := True,  _
    AllowMultiple := False)> _
Public MustInherit Class ActionFilterAttribute _
    Inherits FilterAttribute _
    Implements IActionFilter, IResultFilter

[AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Method, Inherited = true, 
    AllowMultiple = false)]
public abstract class ActionFilterAttribute : FilterAttribute, 
    IActionFilter, IResultFilter

[AttributeUsageAttribute(AttributeTargets::Class|AttributeTargets::Method, Inherited = true, 
    AllowMultiple = false)]
public ref class ActionFilterAttribute abstract : public FilterAttribute, 
    IActionFilter, IResultFilter

The ActionFilterAttribute type exposes the following members.

Constructors

	Name	Description
	ActionFilterAttribute	Initializes a new instance of the ActionFilterAttribute class.

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Properties

	Name	Description
	Order	Gets or sets the order in which the action filters are executed. (Inherited from FilterAttribute.)
	TypeId	When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)

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Methods

	Name	Description
	Equals	Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Returns the hash code for this instance. (Inherited from Attribute.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	IsDefaultAttribute	When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
	Match	When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	OnActionExecuted	Called by the MVC framework after the action method executes.
	OnActionExecuting	Called by the MVC framework before the action method executes.
	OnResultExecuted	Called by the MVC framework after the action result executes.
	OnResultExecuting	Called by the MVC framework before the action result executes.
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Explicit Interface Implementations

	Name	Description
	_Attribute.GetIDsOfNames	Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
	_Attribute.GetTypeInfo	Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
	_Attribute.GetTypeInfoCount	Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
	_Attribute.Invoke	Provides access to properties and methods exposed by an object. (Inherited from Attribute.)

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Remarks

Typically, you create an action filter by creating an attribute class that inherits from the abstract FilterAttribute class. Some built-in action filters, such as AuthorizeAttribute and HandleErrorAttribute, inherit from the FilterAttribute class. The action filters that derive from FilterAttribute are always called before the action method runs.

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

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

Examples

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
    Inherits ActionFilterAttribute

    Public Overrides Sub OnActionExecuting(ByVal filterContext As ActionExecutingContext)
        filterContext.HttpContext.Trace.Write("(Logging Filter)Action Executing: " + _
                filterContext.ActionDescriptor.ActionName)

        MyBase.OnActionExecuting(filterContext)
    End Sub

    Public Overrides Sub OnActionExecuted(ByVal filterContext As ActionExecutedContext)
        If Not filterContext.Exception Is Nothing Then
            filterContext.HttpContext.Trace.Write("(Logging Filter)Exception thrown")
        End If

        MyBase.OnActionExecuted(filterContext)
    End Sub
End Class

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);
    }
}

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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