The name ‘InitializeControl’ does not exist in the current context

You may just receive an error like so.
"The name ‘InitializeControl’ does not exist in the current context” – Visual Web Part (Sandboxed) bug and how to fix it

in Visual Studio in a SharePoint Visual Web Part 2012 in a Sandboxed solution.

My error was a "'" as in "'<%@ Assembly Name="$SharePoint.Project.AssemblyFullName$" %>"
instead of "<%@ "

Sorted.