I need to initialize the text attribute of the text box element with a property from some where else when actually I can simply do this from code but it will be much more convenient if it possible to do it like this:
<asp:TextBox runat="server" Text="<%= new ContextItem("title").Value %>" />
Unfortunately the above can't be done..
The issue is that this text box element repeats it self several times in the page and my question is:
Are there any suggestions how to make it cleaner then to write it again and again in the code behind?
Thank,
Adler
OK so the basic problem here is that if you use an inline expression you can NOT use it to set a property of a server-side control outside of a binding context (using a binding expression). I have inferred that this is probably because of the timing of the evaluation of these inline expressions. You can, however, render client-side markup in this way. If you want to keep the functionality purely in your aspx file, this is the way to do it.
Edit: Based on input from Justin Keyes, it appears it IS possible to use a binding expression to set the property. You need to manually invoke Page.DataBind() to trigger the textbox to evaluate the expression (see answer below).
For instance this:
<asp:Label ID="lbl" runat="server" Text="<%= Now.ToShortDateString() %>" />
Will produce this output:
<%= Now.ToShortDateString() %>
On the other hand this:
<%= "<span>" & Now.ToShortDateString() & "</span>"%>
Will produce this output:
7/27/2011
The "normal" way to solve this problem is just to set the Label.Text properties in a Page.Load event handler or another appropriate event handler depending on your needs, as below. This is the way I believe most people would prefer to do it, and is most easily understandable in my opinion.
Markup:
<asp:Label ID="lbl" runat="server" />
Code:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
lbl.Text = Now.ToShortDateString()
End Sub
Option 1: don't use server controls
If you aren't accessing the value on the server, just use plain HTML instead of an ASP.NET server control:
<input ID="Textbox1" Type="Text"
Value='<%= new ContextItem("title").Value %>' />
Option 2: use Page.DataBind()
If you change your code to use <%# instead of <%= (as below) and call Page.DataBind(), it will work (I've tested it). Change your markup to this:
<asp:TextBox runat="server" Text="<%# new ContextItem("title").Value %>" />
And in your logic, call Page.DataBind() in the Load event like this:
protected void Page_Load(object sender, EventArgs e) {
Page.DataBind();
}
Even though the TextBox is not contained in a typical "data bound" control such as a Repeater or GridView, calling DataBind() on a control will force it to evaluate <%# ... %> statements.
The Moof's comment (below) is correct. This post also mentions Page.DataBind().
You can set the text on a page in a similar way.
<asp:TextBox id="TextBox1" runat="server" Text='<%#GetValue('Title)%>' />
But in order for this to work, you will need to DataBind the control on Page_Load. For multiple TextBox controls you could just loop through each and databind them so that you do not have to hard code the databinding of each.
I am not sure what your ContextItem is though, so you would have to modify my code.
The short answer is NO, you can only use this kind of code with databindings, that means inside a GridView for example. But you can use this in the head section.
I use it to prefix my urls sometimes with something predefined. Example
<script src="<%=Utils.GetGeneralPrefix()%>/Scripts/jquery-1.4.1.min.js" type="text/javascript"></script>
In that case it works.
Hope it helps.
90% of the time when I try this I have to use single quotes ('') instead of double quotes ("") around the <%%>. Give that a try before you spend too much time on anything else.
