Adding a user control after a postback within an UpdatePanel, followed by another postback - how to get the input of controls within the user control?

I have a user control which is being loaded to the page dynamically after performing a postback within an UpdatePanel.

Then I'm performing another postback for saving, where I would like to access the user input for the controls within that user control (for example, a grid with a checkbox in every row).

A simplified example if this scenario would be something as follows:

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <div><asp:Button ID="ButtonAdd" runat="server" Text="Add User Control" OnClick="ButtonAdd_OnClick" /></div>
        <div id="divContent" runat="server"></div>
    </ContentTemplate>
</asp:UpdatePanel>
<asp:UpdatePanel ID="UpdatePanel2" runat="server">
    <ContentTemplate>
    开发者_Python百科    <div><asp:Button ID="ButtonSave" runat="server" Text="Save" OnClick="ButtonSave_OnClick" /></div>
    </ContentTemplate>
</asp:UpdatePanel>

And:

protected void ButtonAdd_OnClick(object sender, EventArgs e)
{
    MyUserControl uc = Page.LoadControl("MyUserControl.ascx") as MyUserControl;
    divContent.Controls.Add(uc);
}

protected void ButtonSave_OnClick(object sender, EventArgs e)
{
    // Hopefully, get controls from within the user control's grid and save their input
}

The problem is that after the save button is clicked, the user control is gone. That's understandable and I have no problem creating and adding it again - but I do want to access the user input and save it. How can I do that?

---

If you want to add controls programatically then choose Page_Load (more preferred) or Page_Init event. You can solve your problem by adding control "statically" (design time) with visible=false and later you may turn on its visibility.

In case you want stick with current approach as in your post, you have to use a trick.

MyUserControl uc;

protected void Page_Load()
{
   if(ViewState["isAdd"]!=null)
    {
       AddControl();
    }
}

void AddControl()
{
    uc = Page.LoadControl("MyUserControl.ascx") as MyUserControl;
    divContent.Controls.Add(uc);
}

protected void ButtonAdd_OnClick(object sender, EventArgs e)
{
    if(ViewState["isAdd"]==null)
        AddControl();
    ViewState["isAdd"]="yes";
}

---

To access the internal controls, you have to expose them with properties or use FindControl.

Also, as you mentioned, you have add dynamic controls back to the page on each postback.

Dynamic Web Controls, Postbacks, and View State