I think the code is correct, but it could be the code is not triggered at all by event.
Can you try Response.Write("test")
and see if it is printed?

If not, when you add a control (ascx), do you use condition if it is not postback?
If yes, try to remove that if condition.
Let me know if this works.

The pop up required a javascript, it can not be done in behind code.
What you can do use a literal control or label control.

Now try to get the url and paste into the control above.
 

ex: Dim str As string = EditUrl("ViewDetailAncment", "ViewDetailAncment", "ViewDetailAncment", "recordID=" + rid) <=== you get the url already

search on the internet how to do a pop up.

then just add the script in your control ex:

Lets say the literal control named litText
Then litText.Text = "<a href='" & str & "'>Pop me up</a>"

Hope this help