Hi,
You can try to do access a web user control that has been placed within a masterpage from a web form by using the findcontrol,
Like below:
UserControl uc = (UserControl)this.Master.FindControl("UC1l1");// UC1l1 is the id of the usercontrol that is on the master page.
Or you also can access the UserControl's controls by using the findcontrol method.
For example:
Button btn = (Button)this.Page.FindControl("ctl00$UC1l1$Button1"); // the Button1 is a button control on the usercontrol.
Hope it helps.
Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Yours sincerely,
Amanda Wang
Microsoft Online Community Support