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OnMethodBoundaryAspect Class
Aspect that, when applied to a method defined in the current assembly, inserts a piece of code before and after the body of these methods.
Inheritance Hierarchy
System.Object
  System.Attribute
    PostSharp.Extensibility.MulticastAttribute
      PostSharp.Aspects.Aspect
        PostSharp.Aspects.MethodLevelAspect
          PostSharp.Aspects.OnMethodBoundaryAspect

Namespace: PostSharp.Aspects
Assembly: PostSharp (in PostSharp.dll) Version: 4.3.31.0 (4.3.31.0)
Syntax
C#
[SerializableAttribute]
public abstract class OnMethodBoundaryAspect : MethodLevelAspect, 
	IOnStateMachineBoundaryAspect, IOnMethodBoundaryAspect, IMethodLevelAspect, IAspect

The OnMethodBoundaryAspect type exposes the following members.

Constructors
  NameDescription
Protected methodOnMethodBoundaryAspect
Initializes a new instance of the OnMethodBoundaryAspect class
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Properties
  NameDescription
Public propertyApplyToStateMachine
Determines how the aspect should behave when it is applied to an iterator or async methods, which are compiled into state machines.
Public propertyAspectPriority
Gets or sets the weaving priority of the aspect.
(Inherited from Aspect.)
Public propertyAttributeExclude
If true, indicates that this attribute removes all other instances of the same attribute type from the set of elements defined by the current instance.
(Inherited from MulticastAttribute.)
Public propertyAttributeInheritance
Determines whether this attribute is inherited
(Inherited from MulticastAttribute.)
Public propertyAttributePriority
Gets or sets the priority of the current attribute in case that multiple instances are defined on the same element (lower values are processed before).
(Inherited from MulticastAttribute.)
Public propertyAttributeReplace
Determines whether this attribute replaces other attributes found on the target declarations.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetAssemblies
Gets or sets the assemblies to which the current attribute apply.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetElements
Gets or sets the kind of elements to which this custom attributes applies.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetExternalMemberAttributes
Gets or sets the visibilities, scopes, virtualities, and implementation of members to which this attribute applies, when the member is external to the current module.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetExternalTypeAttributes
Gets or sets the visibilities of types to which this attribute applies, when this type is external to the current module.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetMemberAttributes
Gets or sets the visibilities, scopes, virtualities, and implementation of members to which this attribute applies.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetMembers
Gets or sets the expression specifying to which members this instance applies.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetParameterAttributes
Gets or sets the passing style (by value, out or ref) of parameters to which this attribute applies.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetParameters
Gets or sets the expression specifying to which parameters this instance applies.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetTypeAttributes
Gets or sets the visibilities of types to which this attribute applies.
(Inherited from MulticastAttribute.)
Public propertyAttributeTargetTypes
Gets or sets the expression specifying to which types this instance applies.
(Inherited from MulticastAttribute.)
Protected propertySerializerType
Gets or sets the Type of the serializer (a type derived from AspectSerializer) used to serialize the aspect instance at build time and deserialize it at runtime.
(Inherited from Aspect.)
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Methods
  NameDescription
Public methodCompileTimeInitialize
Method invoked at build time to initialize the instance fields of the current aspect. This method is invoked before any other build-time method.
(Inherited from MethodLevelAspect.)
Public methodCompileTimeValidate(Object)
Method invoked at build time to ensure that the aspect has been applied to the right target.
(Inherited from MethodLevelAspect.)
Public methodCompileTimeValidate(MethodBase)
Method invoked at build time to ensure that the aspect has been applied to the right target.
(Inherited from MethodLevelAspect.)
Protected methodCreateAspectConfiguration
Method invoked at build time to create a concrete AspectConfiguration instance specifically for the current Aspect type.
(Overrides Aspect.CreateAspectConfiguration().)
Public methodGetAspectConfiguration
Method invoked at build tome to get the imperative configuration of the current Aspect.
(Inherited from Aspect.)
Public methodOnEntry
Method executed before the body of methods to which this aspect is applied.
Public methodOnException
Method executed after the body of methods to which this aspect is applied, in case that the method resulted with an exception.
Public methodOnExit
Method executed after the body of methods to which this aspect is applied, even when the method exists with an exception (this method is invoked from the finally block).
Public methodOnResume
Method executed when a state machine resumes execution after an yield return or await statement.
Public methodOnSuccess
Method executed after the body of methods to which this aspect is applied, but only when the method successfully returns (i.e. when no exception flies out the method.).
Public methodOnYield
Method executed when a state machine yields, as the result of an yield return or await statement.
Public methodRuntimeInitialize
Initializes the current aspect.
(Inherited from MethodLevelAspect.)
Protected methodSetAspectConfiguration(AspectConfiguration, Object)
Method invoked at build time to set up an AspectConfiguration object according to the current Aspect instance and a specified target element of the current aspect.
(Inherited from MethodLevelAspect.)
Protected methodSetAspectConfiguration(AspectConfiguration, MethodBase)
Method invoked at build time to set up an AspectConfiguration object according to the current Aspect instance and a specified target element of the current aspect.
(Overrides MethodLevelAspect.SetAspectConfiguration(AspectConfiguration, MethodBase).)
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Extension Methods
  NameDescription
Public Extension MethodQueryInterface<T>
Gets the implementation of a specified interface for the specified object.
(Defined by QueryInterfaceExtensions.)
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Remarks

The OnMethodBoundaryAspect aspect results in the target method to be wrapped into a try ... catch ... finally block. You can implement four advices: OnEntry(MethodExecutionArgs), executed at the beginning of the block; OnSuccess(MethodExecutionArgs), executed only when the method is successful (i.e. does not result in an exception); OnException(MethodExecutionArgs), invoked when the method results in an exception; and OnExit(MethodExecutionArgs), always executed after method execution (whether the method resulted in an exception or not).

Schematically, the aspect transforms the original method as follows:

C#
int MyMethod(object arg0, int arg1)
{
   OnEntry();
   try
   {
    // Original method body. 
    OnSuccess();
    return returnValue;
  }
  catch ( Exception e )
  {
    OnException();
  }
  finally
  {
    OnExit();
  }
}

Note that this code is only schematic; actually generated instructions are more complex because they have to cope with parameter boxing and control flow modification, among others.

An object of type MethodExecutionArgs is passed to every advice of this aspect. This object allows you to:

  • Get or set arguments . Input and output arguments are available on the property Arguments . You can change output ( out ) and by-reference ( ref ) arguments, but not input arguments. If you need to modify arguments passed by value, consider using a MethodInterceptionAspect . (see property );
  • Get the current exception . The current exception is available on property Exception , but from the OnException(MethodExecutionArgs) advice. You cannot replace the exception by setting this property. Throw a new exception from the aspect if you need to replace the current exception.
  • Get or set the return value . The return value is available on the ReturnValue property.
  • Change the method control flow . You can change the value of the FlowBehavior property to specify whether the target method should execute after the execution of the current advice. This may be useful to implement a caching aspect or an exception handler.
  • Share state between advices . You can use the MethodExecutionTag property to store state between the execution of different advices related to the same execution of a method. For instance, you can store a cache key in OnEntry(MethodExecutionArgs) and find it back on OnSuccess(MethodExecutionArgs) . Using MethodExecutionTag is the only way to share state that is both thread-safe and reentrant. All other implementations are buggy.

Note Note
All classes implementing IAspect should typically be marked as serializable using the custom attribute SerializableAttribute . Fields that are only used at runtime (and unknown at compile-time) should be carefully marked with the custom attribute NonSerializedAttribute . When PostSharp is used on a platform that does not support aspect serialization (such as .NET Compact Framework, Silverlight, or Windows Phone), or when another aspect serializer is used, it is not necessary to mark the aspect class as serializable. For more information, see Aspect Serialization .

See Also