How to do two way binding in code behind/in C#?

I have a stepper control and I initializes it with value 5 in my viewmodel and here is the binding

Stepper stepper = new Stepper { Increment = 1};
stepper.SetBinding(Stepper.ValueProperty. new Binding(path: 'StepperValue', mode: BindingMode.TwoWay));

I have a label which is also listening to this StepperValue to display the values as the user presses + or - button. With the above code and having the initial value to set to 5, I was expecting when the user presses + for the first time, the StepperValue should turn to 6, but instead it turn to 1 as if the initial value is set to 0. Is there something I am doing wrong?

Also, can someone point me to the code where I can implement command pattern for stepper click event in the code behind? (I stopped using XAML purely because there is no intellisense support today).