[Solved] How to prevent Eval() from being called unless the containing Panel is Visible?

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I have a page where we want to either display an image of a product if the image exists on the disk of the web server, or if not, we want product features description text displayed.

My approach was to implement two asp:Panel controls, one to hold the <div> containing the asp:ListView that calls the DB to display the product feature text; and another asp:Panel to display the <div> that contains the <img> for the image.

I want to also, though, avoid calling the Eval() function to call into the DB to get the feature text unless its containing asp:Panel is displayed.

Am I doing something wrong with the following code?

ASP

<asp:Panel runat="server" ID="pnlFeaturesText" Visible="false" CssClass="FeaturesList">
                    <div id="divFeaturesText">
                        <asp:ListView runat="server" ID="lstFeatures">
                            <layouttemplate>
                                <ul>
                                    <li  runat="server" id="itemPlaceholder" />
                                </ul>
                            </layouttemplate>
                            <itemtemplate>
                                <ul><li style="margin-removed 15px;">
                                    <asp:Label runat="server" Text='<%# if (pnlFeaturesText.Visible) { Eval("Feature1") } %>' Style="font-weight: 700;" Font-Names="Verdana" /><br />
                                    <asp:Label runat="server" Text='<%# if (pnlFeaturesText.Visible) { Eval("Benefit") } %>' Font-Names="Verdana" /></li></ul>
                            </itemtemplate>
                        
                    </div>

I am specifically talking about the lines

ASP

<asp:Label runat="server" Text='<%# if (pnlFeaturesText.Visible) { Eval("Feature1") } %>' Style="font-weight: 700;" Font-Names="Verdana" />

I can't use an if statement in the Text property for some reason; the page returns the exception "Invalid expression: if".

What would be a workaround? Set the text by hand, in my code? What's the syntax for that?

Thanks!

Brian

Posted 1-Sep-11 5:38am

Brian C Hart86.6K

Updated 1-Sep-11 6:04am

v2

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#realJSOP · Accepted Answer · 2011-09-01T05:51:00

Write a method in your code behind, put the if in there, and call your method from the markup.

C#

public void ControlEval(string evalThis)
{
    if (pnlFeaturesText.Visible)
    {
        Eval(evalThis);
    }
}

and then you can do this:

XML

<asp:Label runat="server" Text='<%# ControlEval("Feature1"); %>' Style="font-weight: 700;" Font-Names="Verdana" /><br />
<asp:Label runat="server" Text='<%# ControlEval("Benefit"); %>' Font-Names="Verdana" /></li></ul>