vb.net - ASP.NET dynamic Command Button event not firing

Question

I'm trying to create Command Buttons dynamically, but clicking the button in question doesn't seem to raise the corresponding CommandButton_Click event. I noticed that in the examples on SO a property is set for Button.OnCommand as well as the CommandName and CommandArgument but it isn't an option in intellisense.

So the question is, what am I doing wrong here (code below without the OnCommand), is it accessed in some other way - if so, why do the examples I've found all show it as .OnCommand?

EDIT: Further to help, I have added the handler however the event is still not firing. The buttons reside in an UpdatePanel and are rebuilt on every postback (along with the handler). I have created a simplified example of what I'm doing which is shown below If the button event fires, it writes "EVENT FIRED" to the txtTestFired Textbox - suffice to say I have never seen that. This is really driving me nuts, any help is very gratefully received.

.aspx file

<form id="frmMain" runat="server">
    <asp:ScriptManager ID="scmAddProducts" runat="server">
    </asp:ScriptManager>
    <asp:updatepanel runat="server">
        <ContentTemplate>
            <asp:TextBox ID="txtProduct" runat="server"></asp:TextBox>
            <br />
            <asp:Button ID="btnAddItem" runat="server" Text="Add Line" />&nbsp;
            <asp:TextBox ID="txtTestFired" runat="server"></asp:TextBox>
            <br />
            <br />
            <asp:Panel ID="pnlAddedLines" runat="server"></asp:Panel>
        </ContentTemplate>
    </asp:updatepanel>
</form>

.aspx.vb file

Protected Sub btnAddItem_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAddItem.Click
    Dim dtItems As New System.Data.DataTable

    If Session("Items") Is Nothing Then
        Dim dcColumn As New System.Data.DataColumn
        dcColumn.DataType = Type.GetType("System.String")
        dcColumn.ColumnName = "Product"
        dtItems.Columns.Add(dcColumn)
        Session("Items") = dtItems
    End If

    dtItems = CType(Session("Items"), System.Data.DataTable)
    Dim drRow As System.Data.DataRow
    drRow = dtItems.NewRow()
    drRow("Product") = txtProduct.Text
    dtItems.Rows.Add(drRow)

    Session("Items") = dtItems
    txtProduct.Text = ""
End Sub
Protected Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
    If Not Session("Items") Is Nothing Then
        Dim dtItems As System.Data.DataTable = CType(Session("Items"), System.Data.DataTable)
        Dim iItemIndex As Integer = 1
        For Each drRow In dtItems.Rows
            Dim btnClose As New Button
            btnClose.ID = "btnClose" & iItemIndex
            btnClose.CssClass = "formCloseButton"
            btnClose.Text = "X"
            AddHandler btnClose.Click, AddressOf Button_Clicked
            pnlAddedLines.Controls.Add(btnClose)
            btnClose = Nothing

            Dim txtProduct = New TextBox
            txtProduct.ID = "txtProduct" & iItemIndex
            txtProduct.CssClass = "formText"
            txtProduct.Text = drRow("Product")
            txtProduct.Columns = "40"
            pnlAddedLines.Controls.Add(txtProduct)
            iItemIndex += 1

            Dim litHR = New Literal
            litHR.Text = "<hr />"
            pnlAddedLines.Controls.Add(litHR)
            litHR = Nothing
        Next
    End If
End Sub
Private Sub Button_Clicked(ByVal sender As Object, ByVal e As System.EventArgs)
    txtTestFired.Text = "EVENT FIRED"
End Sub

Answer 1

You have to wire it up like this (in C#):

myButton.Click += new EventHandler(this.Button_Clicked);

Alternatively you can inject the attribute --> onclick = "Button_Clicked" like this:

myButton.Attributes.Add("onclick", "Button_Clicked");

If you want it in VB.NET go to this page and knock yourself out - I could do it for you but what's the point :)

EDIT: keep in mind you'll have to re-wire the event-handler (as shown above) every page-load.

EDIT: OK - I see the problem now that you added the rest of the code. You are wiring up the event handler on pre_render. Event handlers are executed just before load_complete, which happens before pre_render. This is why you event_handler doesn't execute: you're adding it too late in the page lifecycle. Put that code in the page_load routine and it should work.