單擊“添加”按鈕后如何重新加載動態添加的用戶控件

Question

我有一個要求，當我單擊父頁面中的“添加”按鈕時，必須動態加載用戶控件。 用戶控件包含文本框，下拉菜單和刪除按鈕。 如果單擊特定用戶控件的“刪除”按鈕，它將被刪除。 一切都很好。 問題是，單擊“添加”按鈕后，頁面將回退，並且用戶控件中的選定值將失去其值。 我需要一種方法來從Code后面獲取所有動態添加的控件，並將其存儲在視圖狀態中，然后在頁面加載中再次將其轉換為用戶控件，並將其添加到頁面中。 請對此提供幫助。

SecondaryDestination.ascx如下所示：占位符將動態加載控件。

<td><asp:Label id="lblSecondary">Secondary Destination</asp:Label></td>     
<td>asp:DropDownList id="ddlSecondary" runat="server" CssClass="ddlbox" AutoPostBack="true"></asp:DropDownList> </td>   
<asp:UpdatePanel ID="updateEmailFtp" runat="server" UpdateMode="Conditional">
<ContentTemplate>
    <asp:PlaceHolder ID="plcEmail" runat="server">
        <table cellpadding="0" cellspacing="0" border="0" class="tbl_form" runat="server" id="tblSecondary">
        </table>    
    </asp:PlaceHolder>
</ContentTemplate>
<Triggers>
    <asp:AsyncPostBackTrigger ControlID="ddlSecondary" EventName="SelectedIndexChanged" />
</Triggers>

用戶控件動態添加控件

protected void ddlSecondary_SelectedIndexChanged(object sender, EventArgs e)
    {
        if(ddlSecondary.SelectedIndex > 0)
        {
            pickerSecondaryViewPresenter = new PickerSecondaryViewPresenter(this);
            DestinationBO secondaryDestination = pickerSecondaryViewPresenter.getSecondaryDestination(int.Parse(ddlSecondary.SelectedItem.Value));

            if(secondaryDestination.DestinationType == "Email")
            {
                HtmlTable tblContent = (HtmlTable)FindControl("tblSecondary");

                Label lblPrimary = new Label();                 
                lblPrimary.Text = "Email Disstribution List";                                       
                HtmlTableCell tcPrimary1 = new HtmlTableCell();
                tcPrimary1.Controls.Add(lblPrimary);

                Label lblPrimaryDistributionList = new Label(); 
                lblPrimaryDistributionList.Text = secondaryDestination.DistributionList;
                HtmlTableCell tcPrimary2 = new HtmlTableCell();
                tcPrimary2.Controls.Add(lblPrimaryDistributionList);

                HtmlTableRow trPrimary = new HtmlTableRow();
                trPrimary.Controls.Add(tcPrimary1);
                trPrimary.Controls.Add (tcPrimary2);                        
                tblContent.Controls.Add(trPrimary);                     
            }
            else
            {
                Label lblFtp = new Label();                 
                lblFtp.Text = "Ftp Host";
                HtmlTableCell tcPrimary1 = new HtmlTableCell();
                tcPrimary1.Controls.Add(lblFtp);

                Label lblFtpHost = new Label();                 
                lblFtpHost.Text = secondaryDestination.FtpHost;                 
                HtmlTableCell tcPrimary2 = new HtmlTableCell();
                tcPrimary2.Controls.Add(lblFtpHost);    

                Button btn = new Button();
                btn.Text = "Connect FTP";
                tcPrimary2.Controls.Add(btn);   

                HtmlTableRow trPrimary1 = new HtmlTableRow();
                trPrimary1.Controls.Add(tcPrimary1);
                trPrimary1.Controls.Add (tcPrimary2);   

                Label lblDirectory = new Label();                   
                lblDirectory.Text = "Ftp Directory";
                HtmlTableCell tcPrimary3 = new HtmlTableCell();
                tcPrimary3.Controls.Add(lblDirectory);

                TextBox txtDirectory = new TextBox();                   
                txtDirectory.Text = "";                 
                HtmlTableCell tcPrimary4 = new HtmlTableCell();
                tcPrimary4.Controls.Add(txtDirectory);

                HtmlTableRow trPrimary2 = new HtmlTableRow();
                trPrimary2.Controls.Add(tcPrimary3);
                trPrimary2.Controls.Add(tcPrimary4);

                tblSecondary.Controls.Add(trPrimary1);      
                tblSecondary.Controls.Add(trPrimary2);

            }

此用戶控件將添加到page1.aspx中：

<div>
<asp:UpdatePanel id ="up1" UpdateMode="conditional">
    <ContentTemplate>
        <uc:DestinationPicker id="destinatioPicker" runat="server" ></uc:DestinationPicker>
    </ContentTemplate>
</asp:UpdatePanel>
</div>
<asp:PlaceHolder ID="divSecondary" runat="server">  
    <ucS:DestinationPickerSecondary id="destinationPickerSecondary" runat="server" ></ucS:DestinationPickerSecondary>       
</asp:PlaceHolder>  

<div>
    <asp:Button id="btnAddSecondary" Text="Add Secondary" runat="server" OnClick="btnAddSecondary_Click"></asp:Button>
</div>

</div>

添加和刪​​除用戶控件可以正常工作：

protected void Page_Load(object sender, EventArgs e)
{    if(IsPostBack)
{
    AddAndRemoveDynamicControls();
}
}

我的問題是，每次單擊添加按鈕以添加動態添加的用戶控件的新實例時，我都需要將所選項目保存在先前添加的用戶控件的下拉列表中

Answer 1

在回發處理期間加載viewstate時，它將視圖狀態中的值與已加載的控件相關聯。 您必須在處理viewstate之前動態地重新加載控件。 我過去在page_init事件中完成了此操作。