Prism not unloading a view

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C#

C#4.0

PRISM

I have a ViewModel that I am implementing the IRegionMemberLifeTime Interface.

public class ReportsViewModel : ViewModelBase, INavigationAware, IRegionMemberLifetime

    {
        public bool KeepAlive
        {
            get { return false; }
        }

To navigate from one view to the other i am calling:

public void Execute(object parameter)
        {
            IRegionManager regionManager = ServiceLocator.Current.GetInstance<IRegionManager>();

            // Show View
            var ModuleView= new Uri("ReportsView", UriKind.Relative);
            regionManager.RequestNavigate("MainRegion", ModuleView);
        }

I have set a breakpoint in the ReportsViewModel but the KeepAlive variable is not getting called.

I am new to Prism and have gone through the documentation. I am not sure what am missing?