Eval in anchor href

Question

I have the following code behind:

protected string VcdControlPanelLink { get; set; }

protected void Page_Load(object sender, EventArgs e) {
    VcdControlPanelLink = "http://www.mywebsite.com";
}

And the following markup:

<a href='<%# Eval(VcdControlPanelLink) %>' target="_blank" title="View the VDC control panel">VDC control panel</a>

But when I run the page, the href tag is rendered as an empty string:

<a title="View the VDC control panel" target="_blank" href="">VDC control panel</a>

I have tried various combinations of markup etc, but cannot get it to work. What am i missing?

Answer 1

If you use data binding expressions <%# ... %> in templates (eg the ItemTemplate of a GridView), data binding is invoked automatically. However, if you use such expressions outside of templates, you need to invoke data binding yourself by calling Control.DataBind() (or this.DataBind() in your case):

protected string VcdControlPanelLink { get; set; }

protected void Page_Load(object sender, EventArgs e) {
    VcdControlPanelLink = "http://www.mywebsite.com";
    this.DataBind();
}

<!-- Note that you do *not* use Eval here! -->
<a href='<%# VcdControlPanelLink %>' target="_blank" ... />

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However, I don't think data binding is the right tool here. Since you are using basic HTML elements (instead of web controls), you can just use an inline ASP.NET expression (no this.DataBind() required):

<a href='<%= VcdControlPanelLink %>' target="_blank" ... />

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In any case, make sure your link does not contain quotes ' , or you are in for some HTML injection. If the value is supplied by the user, don't forget to HtmlEncode and sanitize it.

Answer 2

Make your property public and access it like this,

public string VcdControlPanelLink { get; set; }

<a href='<%= VcdControlPanelLink %>' target="_blank" title="View the VDC control panel">VDC control panel</a>