ASP.NET:

I am new to ASP.NET, and am faced with a relatively easy task -- to make a change to an existing textbox control.

I am seeing two methods that manipulate this textbox control -- OnPreRender() and SetupGuiMap().
I am not sure in which method I should make my necessary changes.

In the OnPreRender(), it appears that the textbox is added:
private GuiMapper _gm = new GuiMapper();
...
_gm.Add( new TextBoxMap(addr.Address1, txtStreet1, lblStreet1));




In the OnPreRender(), it appears that the visibility property is touched upon:

txtStreet1.Visible = true;




I am not sure if these are standard methods in ASP.NET, but I believe these methods have a certain order in which they are called. So if for example, I change a property in one method, it might potentially be overridden in another method.