c# - How to make own event handler? -

i making windows forms project in c#, in made class labelx inherits system.windows.forms.label, added property mass of float type

now, question how can handle, when value of mass changed.

e.g.:
when user enter value zero or less zero
want fire message "mass can't 0 or negative"

if interpreting correctly, there 2 parts this. first, need detect invalid values , throw exceptions. second, need raise event when property changes. can achieved follows.

private float mass; public float mass {         {         return this.mass;     }      set     {         if (value <= 0.0f)         {             throw new argumentoutofrangeexception("mass cannot 0 or negative.");         }          if (this.mass != value)         {             this.mass = value;             onmasschanged(eventargs.empty);         }     } }  public event eventhandler masschanged;  protected virtual void onmasschanged(eventargs args) {     var handler = this.masschanged;     if (handler != null)     {         handler(this, args);     } } 

to show message if invalid entry made, should put try \ catch block around call set mass , catch argumentoutofrangeexception.