Question

Is there a way pass values from other controls (e.g. “selected value of dropdownlist”, “value from query string”) to a User Control using a property within the tag itself and NOT from the code behind?

Answer 1

Yes you can, you just need to use the <% %> in the presentation code. Your code would look something like this:

<asp:DropDownList id="ddlFoo" runat="server">
    ...
</asp:DropDownList>
<asp:TextBox id="txtBar" runat="server" Text='<%# ddlFoo.SelectedValue %>' />

<%-- For query string --%>
<asp:TextBox id="txtBar" runat="server" 
    Text='<%# Request.QueryString["Key_Value"] %>' />

The SO post In ASP.Net, what is the difference between <%= and <%# gives a good listing of the different binding mechanisms you can use.