Hyperlinked Images in ASP.NET GridView

Problem to Solve

A common development task is to place inside GridView the image corresponding to some "Image_URL" typically stored in the data field of underlying database, which is "hyperlinked" to another "Target_URL" also stored in the database. Image OnClick event should open the target web page. If image is missing, then the alternative text should serve as a hyperlinked text.

Three possible solutions pertinent to the ASP.NET GridView control are described below:

1. TemplateField with Hyperlink and img Element

Listing 1

<asp:TemplateField>
    <ItemTemplate>
        <asp:HyperLink runat="server" NavigateUrl='<%# Eval("Wiki_URL") %>'
Target="_blank">
            <img src='<%# Eval("Image_URL") %>'  alt="Read online" />
        </asp:HyperLink>
    </ItemTemplate>
</asp:TemplateField>

2. TemplateField with ImageButton

This technique, even though it provides the minimum coding and fairly robust results, is not recommended as it uses PostBack and, thus, requires the server "round-trip", dramatically degrading the responsiveness of RIA and negatively impacting the overall user experience (it's brought here mostly for didactic purpose).

Listing 2

<asp:TemplateField>
    <ItemTemplate>
            <asp:ImageButton runat="server" ImageUrl='<%# Eval("Image_URL") %>'
            PostBackUrl='<%# Eval("Target_URL") %>' AlternateText="Read online" />
    </ItemTemplate>
</asp:TemplateField>

3. TemplateField with ImageButton and Javascript window.open Added to onClick

This method requires some additional JavaScript coding, but provides maximum flexibility in terms of formatting the target window to be opened on image click event:

Listing 3

<itemtemplate>
 <asp:ImageButton ID="ImageButton1" runat="server" 
 ImageUrl='<%# Eval("Image_URL") %>' 
                        OnClientClick='<%# String.Format
            ("javascript:return openTargetURL(\"{0}\")", 
            Eval("Target_URL")) %>'  AlternateText="Read online" />
</itemtemplate>

JavaScript Snippet to be Added to head Section

This sample JavaScript code snippet allows opening target web page in new browser window with customized appearance set programmatically:

<script type="text/javascript">
    function openTargetURL(url) 
    { window.open(url, "newWindow", "resizable=1,menubar=0,toolbar=0,scrollbars=1"); }
</script>

Design Notes: Server Side Image Rendering

Be aware that pertinent to Listing 1, the image is rendered as "img" element, while in two other cases it is rendered as "input type="image" element. Corresponding sample CSS3 code snippet in Listing 4 shows the best practices addressing these differences.

Listing 4

<style type="text/css">
    /* image rendered as img element within table */
    img { width:200px; }
    /* image rendered as <input> element within table */
    input[type="image"] {width:200px; }
</style>

Image Decoration via HTML5/CSS3

Various aesthetic enhancement techniques, namely single and double borders, borders with inset shadows and color gradients could be applied to the image as described in [1].

References

1. Add Image Borders using HTML5/CSS3[^]
2. Online Slide Show as pure HTML5 / CSS3 solution: NO Javascript[^]