Usercontrol with ajax update panel causes null reference exception.

[Wayne Brantley]

If you expose a public property of a usercontrol that accesses an object on
the user control it will give a null reference exception when you wrap that
in an update panel.

Others are having the same problem. Here is a complete example:
http://forums.asp.net/thread/1555836.aspx

Related to this: (But I am not doing dynamic user control creation)
http://www.eightpence.com/null-controls-inside-of-an-updatepanel-in-aspnet-atlas/

 

[Walter Wang [MSFT]]

Hi Wayne,

I cannot seem to reproduce the issue you mentioned on asp.net forum. I've
created following simple WebUserControl and it's working fine on a WebForm:

<%@ Control Language="C#" ClassName="WebUserControl" %>

<script runat="server">

protected void Button1_Click(object sender, EventArgs e)
{
// Label1.Text = DateTime.Now.ToString();
LabelText = DateTime.Now.ToString();
}

public string LabelText
{
get { return Label1.Text; }
set { Label1.Text = value; }
}

</script>


<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click"
Text="Button" />
</ContentTemplate>
</asp:UpdatePanel>


Please note that I'm not adding a ScriptManager onto the UserControl since
only one ScriptManager instance can exist on a WebForm; therefore the
ScriptManager will always be added to the WebForm.

I've also tried to use a MasterPage and still not able to reproduce it.

Would you please post a complete code listing that could reproduce the
issue? Thanks.


Sincerely,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

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[Walter Wang [MSFT]]

Hi Wayne,

Since a web page can contain only one ScriptManager control (either
directly on the page itself or indirectly inside a nested or parent
component), you can use ScriptManagerProxy
(http://ajax.asp.net/docs/mref/T_System_Web_UI_ScriptManagerProxy.aspx)
when you're using UpdatePanel on a content page or a web user control.


Regards,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

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