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IWebEventCustomEvaluator Interface

Evaluates whether an event should be sent to the related provider for processing.

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

'Declaration
Public Interface IWebEventCustomEvaluator

The IWebEventCustomEvaluator type exposes the following members.

  NameDescription
Public methodCanFireEvaluates whether an event should be raised.
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ASP.NET health monitoring allows production and operations staff to manage deployed Web applications. The System.Web.Management namespace contains the health-event types responsible for packaging application health-status data and the provider types responsible for processing this data. It also contains supporting types that help during the management of health events.

This interface allows enabling or disabling the firing of a specific event. This is especially useful when you implement your own custom event and want to control the rate at which it is sent to the related provider for processing.

NoteNote

This interface does not control how often the event is raised. It only controls how often the event information is sent to the provider for processing.

The following code example shows how to derive from the IWebEventCustomEvaluator interface when creating a custom event.

Imports System
Imports System.Text
Imports System.Web
Imports System.Web.Management


Public Class SampleWebBaseEvent
    Inherits System.Web.Management.WebBaseEvent
    Implements System.Web.Management.IWebEventCustomEvaluator


    Private customCreatedMsg, customRaisedMsg As String 

    ' Store firing record info. 
    Private Shared firingRecordInfo As String 

    ' Implements the IWebEventCustomEvaluator.CanFire  
    ' method. It is called by the ASP.NET if this custom 
    ' type is configured in the profile 
    ' element of the healthMonitoring section. 
    Public Function CanFire( _
    ByVal e As System.Web.Management.WebBaseEvent, _
    ByVal rule As RuleFiringRecord) As Boolean _
    Implements System.Web.Management.IWebEventCustomEvaluator.CanFire

        Dim fireEvent As Boolean 
        Dim lastFired As String = _
            rule.LastFired.ToString()
        Dim timesRaised As String = _
            rule.TimesRaised.ToString()

        ' Fire every other event raised.
        fireEvent = _
        IIf(rule.TimesRaised Mod 2 = 0, True, False)

        If fireEvent Then
            firingRecordInfo = String.Format( _
            "Event last fired: {0}", lastFired) + _
            String.Format( _
            ". Times raised: {0}",  timesRaised) 

        Else
            firingRecordInfo = String.Format( _
            "Event not fired. Times raised: {0}", _
            timesRaised)
        End If 

        Return fireEvent

    End Function 'CanFire


    ' Invoked in case of events identified only by  
    ' their event code. 
    Public Sub New(ByVal msg As String, _
    ByVal eventSource As Object, _
    ByVal eventCode As Integer)
        MyBase.New(msg, eventSource, eventCode)
        ' Perform custom initialization.
        customCreatedMsg = String.Format( _
        "Event created at: {0}", DateTime.Now.TimeOfDay.ToString())

    End Sub 'New 


    ' Invoked in case of events identified by their  
    ' event code.and related event detailed code. 
    Public Sub New(ByVal msg As String, _
    ByVal eventSource As Object, _
    ByVal eventCode As Integer, _
    ByVal eventDetailCode As Integer)
        MyBase.New(msg, eventSource, _
        eventCode, eventDetailCode)
        ' Perform custom initialization.
        customCreatedMsg = String.Format( _
        "Event created at: {0}", DateTime.Now.TimeOfDay.ToString())

    End Sub 'New 


    ' Raises the SampleWebBaseEvent. 
    Public Overrides Sub Raise()
        ' Perform custom processing. 
        customRaisedMsg = String.Format( _
        "Event raised at: {0}", DateTime.Now.TimeOfDay.ToString())

        ' Raise the event. 
        MyBase.Raise()

    End Sub 'Raise

    ' Raises the SampleWebBaseEvent. 
    Public Sub CustomRaise(ByVal evnt _
    As System.Web.Management.WebBaseEvent)

        ' Raise the event.
        Raise(evnt)

    End Sub 'CustomRaise


    ' Gets the event code. 
    Public Function GetEventCode(ByVal detail _
    As Boolean) As Integer 
        Dim eCode As Integer 

        If Not detail Then 
            ' Get the event code.
            eCode = EventCode
            ' Get the detail event code. 
        Else
            eCode = EventDetailCode
        End If 
        Return eCode

    End Function 'GetEventCode


    ' Gets the event sequence. 
    Public Function GetEventSequence() As Long 
        ' Get the event sequence. 
        Dim eventSequence As Long = eventSequence
        Return eventSequence

    End Function 'GetEventSequence



    ' Gets the event source. 
    Public Function GetEventSource() As [Object]
        ' Get the event source. 
        Dim [source] As [Object] = Me.EventSource
        Return [source]

    End Function 'GetEventSource

    ' Gets the event time. 
    Public Function GetEventTime() As DateTime
        ' Get the event source. 
        Dim eTime As DateTime = EventTime
        Return eTime

    End Function 'GetEventTime

    ' Gets the event time. 
    Public Function GetEventTimeUtc() As DateTime
        ' Get the event source. 
        Dim eTime As DateTime = EventTimeUtc
        Return eTime

    End Function 'GetEventTimeUtc

    ' Gets the event sequence. 
    Public Function GetEventMessage() As String 
        ' Get the event message. 
        Dim eventMsg As String = Message
        Return eventMsg

    End Function 'GetEventMessage

    ' Gets the current application information. 
    Public Function GetEventAppInfo() As WebApplicationInformation
        ' Get the event message. 
        Dim appImfo As WebApplicationInformation = _
        ApplicationInformation
        Return appImfo

    End Function 'GetEventAppInfo

    ' Implements the ToString() method. 
    Public Overrides Function ToString() As String 
        Return MyBase.ToString()

    End Function 'ToString

    ' Implements the ToString(bool, bool) method. 
    Public Function customToString(ByVal includeAppInfo As Boolean, _
    ByVal includeCustomInfo As Boolean) As String 
        Return MyBase.ToString(includeAppInfo, includeCustomInfo)

    End Function 'customToString

    ' Gets the event identifier. 
    Public Function GetEventId() As Guid
        Dim evId As Guid = EventID
        Return evId

    End Function 'GetEventId


    'Formats Web request event information. 
    Public Overrides Sub FormatCustomEventDetails( _
ByVal formatter As WebEventFormatter)
        MyBase.FormatCustomEventDetails(formatter)

        ' Add custom data.
        formatter.AppendLine("")

        formatter.IndentationLevel += 1

        formatter.TabSize = 4

        formatter.AppendLine("*SampleWebBaseEvent Start *")
        formatter.AppendLine("Custom information goes here")
        formatter.AppendLine("* SampleWebBaseEvent End *")
        ' Display custom event timing.
        formatter.AppendLine(customCreatedMsg)
        formatter.AppendLine(customRaisedMsg)
        formatter.IndentationLevel -= 1

    End Sub 'FormatCustomEventDetails

End Class 'SampleWebBaseEvent

The following is an excerpt of the configuration file that enables ASP.NET to use the CanFire method to decide whether the raised event must be sent to the provider for processing.

<healthMonitoring 
  heartBeatInterval="0" enabled="true">

    <providers>
      <add name="SampleWebEventProvider" 
        type="SamplesAspNet.SampleEventProvider, webeventprovider, Version=1.0.1741.20369, Culture=neutral, PublicKeyToken=cf85aa6c978d9dea, processorArchitecture=MSIL" />
    </providers>

    <profiles>
      <add 
        name="Custom" 
        minInstances="1" 
        maxLimit="Infinite" 
        minInterval="00:00:00" 
        custom ="SamplesAspNet.SampleWebRequestEvent,webrequestevent" 
        />
    </profiles>

    <eventMappings>

      <add name="SampleWebRequestEvent" type="SamplesAspNet.SampleWebRequestEvent,webrequestevent, Version=1.0.1759.20533, Culture=neutral, PublicKeyToken=0d72899b07049076, processorArchitecture=MSIL" />

    </eventMappings>

    <rules>
      <clear />

        <add name="Custom Web Request Event" 
          eventName="SampleWebRequestEvent"
          provider="SampleWebEventProvider" profile="Custom" />
    </rules>

</healthMonitoring>

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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