Web Forms :: When To Wire Up Event Handlers For Dynamically Loaded User Controls

Jul 15, 2010

I have a situation where I dynamically load one of twenty user controls at a time in an ASP.net web page. Based on much reading I've done, I understand that I am to reload the user control upon postback via the Page_Init event handler. This I've done and it seems to work fine.

But now I would like to wire up assorted controls in the user controls such that when the value of each is changed, an event is fired and the web page is notified. Here's an example of how I'm doing that:

userControl.NewData_Handler += new EventHandler(UserControl_NewData_Handler);

There's a problem though. Because the user control is being done in Page_Init (ie. before Page_Load) I don't believe that a line of code such as the one above can function yet.

So I'm wondering what the best practice to do this is. It occurred to me that perhaps I could execute the line in the Page_Load event handler but I'm not sure if that's correct or not.

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I'm following this article to load controls dynamically: http://msdn.microsoft.com/en-us/magazine/cc748662.aspx#id0070065.

Second Update:
I also set the same control ID when I load the user control at first time and on each reaload.

Maybe I can use another method to store these values like input hidden fields or Cache. I've choosen ViewState because I don't want to overload server with Session values for each user.

Third update:

I load the controls with this code:

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<div id="divHeader">
<asp:Button ID="Edit" runat="server" Text="Editar" onclick="Edit_Click" />
<div id="leftColumn">
<asp:UpdatePanel ID="UpdatePanelLeft" runat="server">
<asp:Label ID="TryText" runat="server"></asp:Label>
<asp:TreeView ID="DestinationTree" runat="server" ImageSet="Simple">
<ParentNodeStyle Font-Bold="False" />
<HoverNodeStyle Font-Underline="True" ForeColor="#5555DD" />
<SelectedNodeStyle Font-Underline="True" ForeColor="#5555DD"
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<asp:TreeNode Text="Raiz" Value="Raiz">
<asp:TreeNode Text="Destino_1" Value="Destino_1">
<asp:TreeNode Text="Punto_1_1" Value="Punto_1_1">
<asp:TreeNode Text="Contenido_1_1_1" Value="Contenido_1_1_1"></asp:TreeNode>
<asp:TreeNode Text="Contenido_1_1_2" Value="Contenido_1_1_2"></asp:TreeNode>
<asp:TreeNode Text="Punto_1_2" Value="Punto_1_2">
<asp:TreeNode Text="Contenido_1_2_1" Value="Contenido_1_2_1"></asp:TreeNode>
<asp:TreeNode Text="Destino_2" Value="Destino_2">
<asp:TreeNode Text="Punto_2_1" Value="Punto_2_1"></asp:TreeNode>
<asp:TreeNode Text="Punto_2_2" Value="Punto_2_2">
<asp:TreeNode Text="Contenido_2_2_1" Value="Contenido_2_2_1"></asp:TreeNode>
<NodeStyle Font-Names="Tahoma" Font-Size="10pt" ForeColor="Black"
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<div id="rightColumn">
<asp:UpdatePanel ID="UpdatePanelRight" runat="server">
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case 3:
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