面板列表中动态创建的下拉列表不允许进行事件处理

我正在尝试创建一个UI，用于创建可以动态填充的行。

我现在可以将一个面板添加到我的列表中，该列表包含一个DropDownList并有一个关联的Remove按钮。

Remove按钮有一个OnClick事件绑定，允许我删除该特定面板。

我在尝试将SelectedIndexChanged事件处理程序绑定到我的DropDownList时遇到问题，但没有。

我怀疑这与我在每次Postback后如何重新创建控件有关。

我并没有要求或期待一个直截了当的"在代码中添加或更改此项"。我真的很想了解我错在哪里，很抱歉问了这么多！：s

protected void Page_Load(object sender, EventArgs e)
{
    //Showing this for the the poster that asked.
    if (!IsPostBack)
    {
        GetClustersFromDB(user);
        BindGrid();
        BindState();            
    }
    if (Session["persistControls"] != null)
    {
        persistControls = (List<Panel>)Session["persistControls"];
        int count = 0;
        foreach (Panel dynamicControl in persistControls)
        {
            DropDownList list = new DropDownList();
            list.ID = "list" + count;
            list.SelectedIndexChanged += new EventHandler(list_SelectedIndexChanged);
            list.AutoPostBack = true;
            list.Items.Add(new ListItem("", "0"));
            list.Items.Add(new ListItem("Title", "1"));
            dynamicControl.ID = "panel" + count;
            Button btnRemove = new Button();
            btnRemove.Click += new EventHandler(btnDelete_Click);
            btnRemove.Text = "Remove";
            btnRemove.CommandArgument = count.ToString();             
            myPlaceholder.Controls.Add(dynamicControl);
            myPlaceholder.Controls.Add(btnRemove);
            count++;
        }
    }
}
protected void btnAdd_Click(object sender, EventArgs e)
{
    try
    {
        DropDownList list = new DropDownList();
        list.SelectedIndexChanged += new EventHandler(list_SelectedIndexChanged);
        list.AutoPostBack = true;
        list.Items.Add(new ListItem("", "0"));
        list.Items.Add(new ListItem("Title", "1"));
        Panel panelContainer = new Panel();
        panelContainer.ID = "panel" + persistControls.Count;
        panelContainer.Controls.Add(list);
        Button btnRemove = new Button();
        btnRemove.Click += new EventHandler(btnDelete_Click);
        btnRemove.Text = "Remove";
        btnRemove.CommandArgument = persistControls.Count.ToString();
        myPlaceholder.Controls.Add(panelContainer); // Pushes the Panel to the page.
        persistControls.Add(panelContainer);// Adds our Panel to the Control list
        myPlaceholder.Controls.Add(btnRemove); // Pushes our Button to the page.
        Session["persistControls"] = persistControls; // put it in the session
    }
    catch
    {
        throw;
    }
}
protected void btnDelete_Click(object sender, EventArgs e)
{
    try
    {
        int deleteThisOne = int.Parse(((Button)sender).CommandArgument);
        persistControls.Remove(persistControls[deleteThisOne]);
        Session["persistControls"] = persistControls;          
        Response.Redirect(Request.Url.ToString());
    }
    catch
    {
        throw;
    }
}
protected void list_SelectedIndexChanged(object sender, EventArgs e)
{
    throw new NotImplementedException();
}
//aspx File Snippets
<asp:Button ID="btnAdd" runat="server" Text="Add Control" onclick="btnAdd_Click" />
<asp:Button ID="btnClear" runat="server" Text="Reset" onclick="btnClear_Click"/>
<asp:PlaceHolder ID="myPlaceholder" runat="server"></asp:PlaceHolder>