Question

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>
        <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?

Answer 1

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";
}