If you want to bind your WPF to an expression, simply create a read-only property whose getter returns your expression.
yes, but a lot of times the expression isn't something you want to name with specific parameters; maybe a name would make sense with unspecified parameters i.e. maybe it would make more sense for it to be a method.
vanilla (non-implicit) C# properties have nothing to do with variables
I meant implicit ones are member variables with the language automatically providing a getter and a setter. They are named values associated with an object. But yeah.
How does binding to XML files work?