The usual examples for asp.net localisation are for the aspx markup page, not for the code behind.
In fact localisation, accessing localisation resource files programmatically, in code behind is also dead simple. You use GetLocalResourceObject() like so:
ctrl.Text = (string)GetLocalResourceObject("myCtrlKey.Text");
ctrl.AnotherAttribute = (string)GetLocalResourceObject("myCtrlKey.AnotherAttribute");
Using LocalResource means that for a page called MyPage.aspx, you have created a resource file called MyPage.aspx.resx and/or MyPage.aspx.{culturename}.resx in the special directory App_LocalResource.
If you like GlobalResources instead of local, use the special directory App_GlobalResource
to hold a resource file called MyResourceFileName.resx and call:
ctrl.Text= (string)GetGlobalResourceObject("MyResourceFileName", "myGlobalKey");
as per http://msdn.microsoft.com/en-us/library/ms227982.aspx
For a bit more of an overview of asp.net localisation, the page at http://msdn.microsoft.com/en-us/library/ms227427.aspx should only take you a few minutes to scan.