Hi Tomasz,
As for the problem you met, it is due to the limitation of expression that
can be used inside ASP.NET server control attribute/tag. The <%= %>
expression is brought from classic ASP for compatible purpose and can only
be used in plain html fragment(at top level of aspx page or ascx user
control).
For ASP.NET server control tag, you can consider the following means to
embed dynamic value:
1. Use <%# ... %like databinding expression, however, you need to call
control.DataBind() at runtime (in page load or init ...) so as to make the
databinding expression get evaluated.
2. In ASP.NET 2.0, there provides a custom Expression Builder
functionality, that can help you define your own custom expression(can be
used inside server control tag/attributes). Here are some articles
introducing this:
#The CodeExpressionBuilder
http://weblogs.asp.net/infinitiesloo...odeExpressionB
uilder.aspx
http://weblogs.asp.net/leftslipper/archive/2007/01.aspx
Hope this helps.
Sincerely,
Steven Cheng
Microsoft MSDN Online Support Lead
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--------------------
>From: "Tomasz J" <oe****@nospam.nospam>
Subject: Strange Custom Control Problem (.Net 2.0)
Date: Wed, 9 Jan 2008 02:15:06 +0100
>
Hello Developers,
I have a control derived from System.Web.UI.WebControls.WebControl.
Control
>has this property:
[Bindable(true), Category("Misc"), Description("value")]
public string Value
{
set { _value = value; }
get { return _value; }
}
protected override void AddAttributesToRender(HtmlTextWriter writer)
{
base.AddAttributesToRender(writer);
writer.AddAttribute("alt", _value);
}
I use my control like this:
<mc:MyControl ID="MyControl" Value="<%=Value %>" runat="server" />
(the page class has protected Value property)
There are no compilation problems, but ASP.Net incorrectly renders alt
attribute:
alt="<%=Value %>"
It seems like it is a problem at compile-time. I cannot use expressions in
control attribute values.
What could be wrong with this picture?
Any hints highly appreciated.
Tomasz J
