Expression handlers in ASP.NET 2.0 are similar to the previous data handling declarative syntax; <%# DataBinder.Eval ( .. ) %>. You can now access various elements out of your web.config or resources files by using these expressions in your markup.
For example, if you need access to a connection string names LocationConnectionString, you would simply type (remember from yesterday, connection strings are in their own section of the web.config):
<%$ connectionstrings: LocationConnectionString %>
This is typically used in things like SqlDataSources.
To access something in the appSettings element, you just do:
<%$ appSettings: MyKey %>
Resources files have been extended greatly and they may actually pose a viable solution for multilingual text management now. So they can now be used in things like labels, textboxs, etc.
For example:
<asp:label id="MyLabel" runat="server" text="<%$ resources: MyKey %>" />
If these expression handles don't provide you with what you need, then you can always write your own. Although, I am not exactly sure how to do that yet.
Read the complete post at http://www.dotnettipoftheday.com/blog.aspx?id=208