Value of textbox in VB code

I have a input texbox named textbox_iuserid in my Web form.
In my VB code when I code the following:
iuserid = textbox_iuserid.text
I get error message: text is not a member of string
If I do not include .text the value of textbox_iuserid is nothing in my VB code when I put a trace.
What am I doing incorrect.