HyperLinkField control does not work in my web form?

This is my HyperLinkField control:

<asp:HyperLinkField DataNavigateUrlFields="link_eve" DataNavigateUrlFormatString="eventReg.aspx?link_eve={0}" DataTextField="link_eve" HeaderText="Register:" DataTextFormatString="Click Here" />
For some reason when I added this:
DataNavigateUrlFormatString="eventReg.aspx?link_eve={0}"


After the above code has been added, there is no hyperlink in the HyperLinkField control. The HyperLinkField is inside of the DetailsView control.
Any suggestion is appreciated?
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