I'm working with the official ASP.NET walthrough series and got stuck on the page: Walkthrough:Creating and Using ASP.NET Master Pages in Visual Web Developer

I have issues with the section: Changing Master Pages Dynamically. I have error messages like:

Error 1 The type 'Master1' already contains a definition for 'CompanyName'

Error 2 Type 'Master1' already defines a member called 'Page_Init' with the same parameter types 

I have googled and binged for a solution to no avail. Can I get a helping hand, please.