get image url from database asp.net VB

Hi,

I have the url of an image stored in my database. How would I apply this URL to an asp:Image tag.

I was thinking something like this, but this doesn't seem to work, this code tells me that name slide1 isn't delared.

code behind:
slide1.ImageUrl = reader_slides.Item("slide").ToString()

page:
<asp:Image ID="slide1" runat="server" />