了解 ASP.NET WebForms 中控件处于生命周期的哪个阶段

从控件的外部，是否可以找出特定控件或页面处于页面生命周期的哪个阶段（初始化、加载、预渲染等）？

例如，在伪代码中：

if myControl.CurrentLifeCycle == Lifecycle.Init
{ do something }

恐怕没有内置函数来检查页面处于哪个页面生命周期阶段。 在不处理页面本身中的所有事件的情况下添加此功能也很困难，因为某些事件受到保护。因此，您还可以从 Control 继承 LifeCycleListener 类，将其添加到构造函数中以监听页面并覆盖所有事件。

如果您只需要公共“阶段”PreInit,Init,Load,DataBinding,PreRender,Unload,Disposed看看下面的方法（VB.Net，但我想你会明白的）：

Public Enum LifeCyclePhase
    AfterPreInit
    AfterInit
    AfterLoad
    AfterDataBinding
    AfterPreRender
    AfterUnload
    AfterDisposed
End Enum

Public Interface ITrackingLifeCycle
    ReadOnly Property GetLifeCycleListener() As LifeCycleListener
End Interface

Public Class LifeCycleListener

    Public Sub New(ByVal ctrl As Control)
        Me._PageListening = ctrl.Page
        AddListener()
    End Sub

    Private _CurrentPhase As LifeCyclePhase
    Private _PageListening As Page

    Public ReadOnly Property CurrentPhase() As LifeCyclePhase
        Get
            Return _CurrentPhase
        End Get
    End Property

    Public ReadOnly Property PageListening() As Page
        Get
            Return _PageListening
        End Get
    End Property

    Private Sub AddListener()
        AddHandler _PageListening.PreInit, AddressOf PreInit
        AddHandler _PageListening.Init, AddressOf Init
        AddHandler _PageListening.Load, AddressOf Load
        AddHandler _PageListening.DataBinding, AddressOf DataBinding
        AddHandler _PageListening.PreRender, AddressOf PreRender
        AddHandler _PageListening.Unload, AddressOf Unload
        AddHandler _PageListening.Disposed, AddressOf Disposed
    End Sub

    Private Sub PreInit(ByVal sender As Object, ByVal e As EventArgs)
        Me._CurrentPhase = LifeCyclePhase.AfterPreInit
    End Sub

    Private Sub Init(ByVal sender As Object, ByVal e As EventArgs)
        Me._CurrentPhase = LifeCyclePhase.AfterInit
    End Sub

    Private Sub Load(ByVal sender As Object, ByVal e As EventArgs)
        Me._CurrentPhase = LifeCyclePhase.AfterLoad
    End Sub

    Private Sub DataBinding(ByVal sender As Object, ByVal e As EventArgs)
        Me._CurrentPhase = LifeCyclePhase.AfterDataBinding
    End Sub

    Private Sub PreRender(ByVal sender As Object, ByVal e As EventArgs)
        Me._CurrentPhase = LifeCyclePhase.AfterPreRender
    End Sub

    Private Sub Unload(ByVal sender As Object, ByVal e As EventArgs)
        Me._CurrentPhase = LifeCyclePhase.AfterUnload
    End Sub

    Private Sub Disposed(ByVal sender As Object, ByVal e As EventArgs)
        Me._CurrentPhase = LifeCyclePhase.AfterDisposed
    End Sub
End Class

此类中的处理程序是在页面本身的处理程序之后调用的，因此如果您检查Page.Init中的CurrentPhase你会得到PreInit。因此我将此阶段称为 AfterPreInit。

Partial Public Class _Default
    Inherits System.Web.UI.Page
    Implements ITrackingLifeCycle

    Private lcl As New LifeCycleListener(Me)

    Public ReadOnly Property GetLifeCycleListener() As LifeCycleListener Implements ITrackingLifeCycle.GetLifeCycleListener
        Get
            Return lcl
        End Get
    End Property

现在，您可以在任何地方检查生命周期阶段，即使没有通过 HttpContext.Current 引用控件：

Public Class FooClass
    Public Shared Sub Foo()
        If Not (HttpContext.Current Is Nothing OrElse HttpContext.Current.Handler Is Nothing) Then
            If TypeOf HttpContext.Current.CurrentHandler Is ITrackingLifeCycle Then
                Dim page As ITrackingLifeCycle = DirectCast(HttpContext.Current.CurrentHandler, ITrackingLifeCycle)
                Dim phase As LifeCyclePhase = page.GetLifeCycleListener.CurrentPhase
            End If
        End If
    End Sub
End Class

这既没有经过充分的测试，也没有被我自己使用，当然可以改进，但也许它对您当前的情况有帮助。