Visual Basic Webform ASP.net

Question

不知道為什么標簽不連續切換。

我把它弄斷了，它表明計數器每次都會重置，因此它應該一直在交換數字，但似乎不起作用

謝謝！

Public Class WebForm2 Inherits System.Web.UI.Page

Dim d As Integer() = {0, 1, 2, 3, 4}
Dim counter As Integer
Public Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not Page.IsPostBack Then
        Label1.Text = d(0)
        Label2.Text = d(1)
        Label3.Text = d(2)
        Label4.Text = d(3)
        Label5.Text = d(4)
    End If
End Sub

Public Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
    Dim hold As Integer
    counter = 0
    hold = d(0)
    Do While counter < 4
        d(counter) = d(counter + 1)
        counter += 1
    Loop
    Label1.Text = d(0)
    Label2.Text = d(1)
    Label3.Text = d(2)
    Label4.Text = d(3)
    Label5.Text = hold
End Sub

Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles Timer1.Tick
    Dim hold As Integer
    counter = 0
    hold = d(0)
    Do While counter < 4
        d(counter) = d(counter + 1)
        counter += 1
    Loop

    Label1.Text = d(0)
    Label2.Text = d(1)
    Label3.Text = d(2)
    Label4.Text = d(3)
    Label5.Text = hold
End Sub

End Class

Answer 1

我對vb.net並不熟悉，但是我之前已經創建過asp.net頁面，所以我在這里進行了有根據的猜測^^

單擊該按鈕時，將發生回發，並且整個頁面將被重新加載，並且再次聲明數組d。

回發后，存儲在數組中的值將丟失。 為了保留數據，可以使用Session或ViewState變量：

屆會

ViewState

正如我所說的，這是為asp.net提供的，但無論如何可能會有所幫助。

編輯：我仍然認為該d數組中的數據丟失了...如果您只剩下該數組並具有如下所示的button_Click事件，該怎么辦：

        String temp = Label1.Text;

        Label1.Text = Label2.Text;
        Label2.Text = Label3.Text;
        Label3.Text = Label4.Text;
        Label4.Text = Label5.Text;
        Label5.Text = temp;

Answer 2

您的名為d的數組（是否有更好的名稱？）在每次頁面加載時都重新聲明（看起來應該如此）。

問題在於您不會在每次頁面加載時都保留調整后的數組值。 相反，您每次都是從頭開始，就像其他人所建議的那樣。

有關在Web窗體應用程序中保留狀態信息的許多有用信息，請參見以下URL。

http://msdn.microsoft.com/zh-CN/library/vstudio/z1hkazw7(v=vs.100).aspx

就您的代碼而言，您可以按照以下方式嘗試進行一些操作，以保留當前數組中的值，同時將其設置為下一次加載。

Public Class WebForm2 Inherits System.Web.UI.Page

    Private _dValues As Integer(19)
    Private _currentValues As Integer(19)
    Private _newValues As Integer(19)
    Private _startIndex As Integer

    Public Sub New()
        _dValues = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19}
        _startIndex = 0
    End Sub

    Protected Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
        If Page.IsPostBack Then 'Load values from form
            For i As Integer = 0 To _currentValues.Length - 1 Step 1
                _currentValues(i) = Request.Form(String.Concat("Hidden", i))
            Next
            _startIndex = Request.Form("StartIndex")
        Else
            _currentValues = _dValues 'First time around
        End If
        Dim position As Integer = _startIndex
        For i As Integer = 0 To _currentvalues.Length - 1 Step 1
            If position >= _newValues.Length Then
                position = 0
            End If
            'Assign the current position in the new array equal to the current sequential value in the previous array
            _newValues(position) = _currentValues(i)
            position += 1
        Next
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        'Increment the counter every post back
        If Page.IsPostBack Then
            _startIndex += 1
        End If

        'Don't allow the counter to go outside the bounds of the array
        If _startIndex >= _currentValues.Length Then
            _startIndex = 0
        End If
        Me.StartIndex.Text = _startIndex 'Assign the value of the hidden field
    End Sub

    Public Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
    'Dynamically set label / hidden data
        For i As Integer = 0 To _newValues.Length - 1 Step 1
            CType(Page.FindControl(String.Concat("Label", i), Label).Text = _currentValues(i)
            CType(Page.FindControl(String.Concat("Hidden", i), Hidden).Text = _newValues(i)
        Next
    End Sub

    Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles Timer1.Tick
    'Dynamically set label / hidden data
        For i As Integer = 0 To _newValues.Length - 1 Step 1
            CType(Page.FindControl(String.Concat("Label", i), Label).Text = _currentValues(i)
            CType(Page.FindControl(String.Concat("Hidden", i), Hidden).Text = _newValues(i)
        Next
    End Sub

End Class

然后以您的形式：

<asp:Hidden ID="StartIndex" runat="server" Value="" />
<asp:Label ID="Label1" runat="server" Value="" />
<asp:Hidden ID="Hidden1" runat="server" Value="" />

<asp:Label ID="Label2" runat="server" Value="" />
<asp:Hidden ID="Hidden2" runat="server" Value="" />
etc...

此代碼（或其至少一個版本）將構建許多標簽和隱藏的輸入字段，這些字段將用於顯示數據和保留數據。 每次發布頁面時，起始索引都會增加，這將更改新值的起始位置。 而當前值將基於從隱藏輸入中回發的內容。