实现数据加载等待页面的VB.NET代码的方法
实现数据加载等待页面的VB.NET代码的方法
在网上看到很多的ASP.NET实现，但没有找到VB.net相关的实现代码，现根据网上的C#的代码整理下，改造成为VB的代码实现。
其中把实现线程的CLASS放在了页面类的内部，你可以根据需要自己改动。运行时只需要创建一个相应的页面，放一一个按钮和一个LABLE（SERVER端控件），就行
Partial Class _Default
Inherits System.Web.UI.Page
Public clkCnt As Integer
Public task As LengthyTask
'Private taskCache As System.Web.Caching.Cache
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
task = CType(Cache.Get("LengthyTask1"), LengthyTask)
'Cache["LengthyTask"]
If task Is Nothing Then
task = New LengthyTask()
Cache.Insert("LengthyTask1", task)
End If
' The task is already running.
If (task.Running) Then
PreparePageWithTaskRunning()
Else
PreparePageWithTaskNotRunning()
End If
End Sub
Private Sub PreparePageWithTaskRunning()
Dim myScript As String
Button1.Enabled = False
Label1.Text = "The task is running now.<br>It started at " + task.LastStartTime.ToString() + "<br>" + (DateTime.Now - task.LastStartTime).Seconds.ToString() + " seconds have elapsed"
' Register the script to refresh the page every 3 seconds.
myScript = "<script>window.setTimeout('document.location.replace(document.location.href);',3000);</script>"
Page.ClientScript.RegisterStartupScript(Me.GetType(), "key", myScript)
End Sub
Private Sub PreparePageWithTaskNotRunning()
Label1.Text = "The task is not running."
If task.FirstRunFinished Then
Label1.Text += "<br>Last time it started at " + task.LastStartTime.ToString() + "<br> and finished at " + task.LastFinishTime.ToString() + "<br>"
If (task.LastTaskSuccessful) Then
Label1.Text += "It succeeded."
Else
Label1.Text += "It failed."
If Not (task.ExceptionOccured Is Nothing) Then
Label1.Text += "<br>The exception was: " + task.ExceptionOccured.ToString()
End If
End If
End If
End Sub
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
If Not task.Running Then
task.RunTask()
PreparePageWithTaskRunning()
End If
End Sub
Class LengthyTask
' A flag to indicate whether the task has run at least once.
Private _firstRunFinished As Boolean = False
Property FirstRunFinished() As Boolean
Get
Return _firstRunFinished
End Get
Set(ByVal firstRunfinished As Boolean)
_firstRunFinished = firstRunfinished
End Set
End Property
' A flag to indicate whether the task is running.
Private _running As Boolean = False
Property Running() As Boolean
Get
Return _running
End Get
Set(ByVal running As Boolean)
_running = running
End Set
End Property
' A flag to indicate whether the last task succeeded or not.
Public _lastTaskSuccessful As Boolean = True
Property LastTaskSuccessful() As Boolean
Get
If _lastFinishTime = DateTime.MinValue Then
Throw New InvalidOperationException("The task has not finished even once.")
End If
Return _lastTaskSuccessful
End Get
Set(ByVal value As Boolean)
_lastTaskSuccessful = value
End Set
End Property
' To store any exception generated during the task.
Private _exceptionOccured As Exception = Nothing
Property ExceptionOccured() As Exception
Get
Return _exceptionOccured
End Get
Set(ByVal value As Exception)
_exceptionOccured = value
End Set
End Property
Private _lastStartTime As Date = DateTime.MinValue
Property LastStartTime() As Date
Get
If _lastStartTime = DateTime.MinValue Then
Throw New InvalidOperationException("The task has not started even once.")
End If
Return _lastStartTime
End Get
Set(ByVal value As Date)
_lastStartTime = value
End Set
End Property
Private _lastFinishTime As Date = DateTime.MinValue
Property LastFinishTime() As Date
Get
If _lastFinishTime = DateTime.MinValue Then
Throw New InvalidOperationException("The task has not finished even once.")
End If
Return _lastFinishTime
End Get
Set(ByVal value As Date)
_lastFinishTime = value
End Set
End Property
' Start the task
Public Sub RunTask()
' Only one thread is allowed to enter here.
SyncLock Me
If (Not _running) Then
_running = True
_lastStartTime = DateTime.Now
Dim t As Threading.Thread = New Threading.Thread(New Threading.ThreadStart(AddressOf Me.ThreadWork))
t.Start()
Else
Throw New InvalidOperationException("The task is already running!")
End If
End SyncLock
End Sub
Public Sub ThreadWork()
Try
' Suppose that we need to run the DTS package here.
' Replace the following line with your code.
Threading.Thread.Sleep(20000)
' Setting successful flag.
_lastTaskSuccessful = True
Catch e As Exception
' Failed.
_lastTaskSuccessful = False
_exceptionOccured = e
Finally
_running = False
_lastFinishTime = DateTime.Now
If (Not _firstRunFinished) Then _firstRunFinished = True
End Try
End Sub
End Class
End Class