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.

Vulpes · Answer

I've just quickly thrown together an example of using INotifyPropertyChanged for your situation.
Notice that initially Temp and WaveLength both have their default values of 0. No exception is thrown if an attempt is made to set a property to an out of range value - the attempt is simply ignored:
using System; using System.ComponentModel;
public class MyClass : INotifyPropertyChanged {   private double prevTemp;   private double temp;     private double prevWaveLength;   private double waveLength;
public double Temp   {      get { return temp; }           set       {         if (temp == value) return;         if (value >= 30 && value         {                     prevTemp = temp;            temp = value;            NotifyPropertyChanged("Temp");          }      }   }
public double PrevTemp   {      get { return prevTemp; }   }
public double WaveLength   {       get { return waveLength; }        set       {          if (waveLength == value) return;         if (value >= 30 && value         {            prevWaveLength = waveLength;            waveLength = value;            NotifyPropertyChanged("WaveLength");          }      }   }
public double PrevWaveLength   {      get { return prevWaveLength; }   }
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string name)   {      if (PropertyChanged != null)      {         PropertyChanged(this, new PropertyChangedEventArgs(name));      }   }
}
class Program {    static void Main()    {       Program p = new Program();       MyClass mc = new MyClass();       mc.PropertyChanged += p.MyClass_PropertyChanged;       mc.Temp = 40;       mc.Temp = 70; // no effect       mc.Temp = 50;       mc.WaveLength = 35;       mc.WaveLength = 25; // no effect         mc.WaveLength = 45;       Console.ReadKey();      }
void MyClass_PropertyChanged(object sender, PropertyChangedEventArgs pcea)    {        MyClass mc = (MyClass)sender;        if (pcea.PropertyName == "Temp")        {           Console.WriteLine("The Temp property has changed from {0} to {1}", mc.PrevTemp, mc.Temp);        }        else        {           Console.WriteLine("The WaveLength property has changed from {0} to {1}", mc.PrevWaveLength, mc.WaveLength);        }     }
}

Vulpes · Answer

Do you mean that you want the event to be fired every time you 'get' or 'set' the property, or only when you  'set' (and change) it?
If it's the latter then you can implement the INotifyPropertyChanged interface which is useful for data binding. See:
http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx