Property validation.

Question

I want to write an event for everytime the property  below is call. I want to validate the property range everytime either property is called you some an event. I want to remember the last state of the member.? Min = 30.0 and Max = 50
       

       public double Temp{ get; set; }


        public double Wavelenght{ get; set; }

Can some send me a tutorial or assist men.