UpdatePanel (ASP), I lose inserted objects when I insert new objects dynamically

Question

I'm trying to insert one object (Panel) after another inside an UpdatePanel type object (by means of a button), this with the aim of forming an array that looks horizontal visually when the user inserts it inside the UpdatePanel. The problem I have is that every time I insert a new object, it deletes the previous one, that is, I insert object 2 and it deletes 1, if I insert object 3 it deletes 2 and so on only inserting an object inside. The two Textboxes that I use are to control the positions and know how many objects I already have inside.

I am using UpdatePanel, precisely to avoid losing those objects that I insert since each object will have a specific action within the array.

How can I avoid losing the objects already inserted?, any idea?

Waiting for your kind comments... Thank you in advance.

This is the code that I use.

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        Dim PanelS As Panel

        Dim pos As Int32 = Val(TextBox1.Text)
        Dim numPanel As Int32 = Val(TextBox2.Text)

        PanelS = New Panel
        PanelS.ID = "pnl" & (numPanel + 1)
        PanelS.Style.Add(HtmlTextWriterStyle.Height, "500px")
        PanelS.Style.Add(HtmlTextWriterStyle.Width, "110px")
        PanelS.Style.Add(HtmlTextWriterStyle.Left, pos.ToString & "px")
        PanelS.Style.Add(HtmlTextWriterStyle.Position, "absolute")
        PanelS.Style.Add(HtmlTextWriterStyle.BackgroundImage, "~/Images/W1.jpg")
        Panel1.Controls.Add(PanelS)
        TextBox1.Text += 110
        TextBox2.Text += 1


    End Sub

Accepted Answer

Hi @LA RC

I think the cause of the problem may be that you didn't increment the counter for the Panel. At the same time, we need to set a variable on the Page_PreInit page to make each Control's ID different. Take TextBox as an example (better display).

Code:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    End Sub
    Protected Sub Page_PreInit(ByVal sender As Object, ByVal e As EventArgs)
        Dim keys As List(Of String) = Request.Form.AllKeys.Where(Function(key) key.Contains("txtDynamic")).ToList()
        Dim i As Integer = 1
        For Each key As String In keys
            Me.Create("txtDynamic" & i)
            i += 1
        Next
    End Sub
    Protected Sub Add(ByVal sender As Object, ByVal e As EventArgs)
        Dim index As Integer = Panel1.Controls.OfType(Of TextBox)().ToList().Count + 1
        Me.Create("txtDynamic" & index)
    End Sub
    Private Sub Create(ByVal id As String)
        Dim txt As TextBox = New TextBox()
        txt.ID = id
        Panel1.Controls.Add(txt)
        Dim lt As Literal = New Literal()
        lt.Text = "
"
        Panel1.Controls.Add(lt)
    End Sub

As for how you want to change the style, just set it yourself.

Result: Panel

Best regards,
Qi You

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Answer

For the control created in the Button1_Click method, the view-state information from a previous request is not restored because it too late to create the control so that the LoadViewState method for the control works properly. That is probably why. Please investigate it.

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UpdatePanel (ASP), I lose inserted objects when I insert new objects dynamically

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