class MasterModel {
     // common info, used in master page.
}

class Page1Model : MasterModel {
     // page 1 model
}

class ModelBase {
     // common info, used in master page.
}

class Page1Model : ModelBase {
     // page 1 model
}

public class ControllerBase : Controller
{
    protected override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        var model = ViewData.Model as ModelBase;

        // set common data here

        base.OnActionExecuted(filterContext);
    }
}