Annoying Error: Make sure that the class defined in this code file matches the 'inherits' attribute,

HI,
I'm working on a MVC3 project, which has some WebForms code files; here is an error I encountered, in a code behind file for a .ascx file:
Make sure that the class defined in this code file matches the 'inherits' attribute, and that it extends the correct base class (e.g. Page or UserControl).    C:\........\Leads\UserControls\PlanPricing.ascx.cs  
Where the line of code that this error hapeens looks like this:
public partial class Leads_UserControls_PlanPricing : System.Web.UI.UserControl
{
...
Also, there is a blue ~ underneath the 1st "o" in "UserControls".
I researched for a month now; there are many posts saying that in the corrsponding .ascx file, if it's website, all you need do is to use "CodeFile", not "CodeBehind" - I tried this, but I still encounte ...