C#

class myClassThatHoldsTheString
{
    const int _myToolTipLength = 50;

    private string _myTooltip;
    public string MyTooltip
    {
        //return the private
        get { return _myTooltip;}
     
        //modify the inbound string if it is too long
        set {
             if (_myTooltip== value)
                 return;

             if (value.Length > _myToolTipLength)
                 _myTooltip= value.Substring(0,myToolTipLength );
             else
                 _myTooltip= value;
             }
     }
}

//to use

myControl.Tootip = myInstance.MyTooltip;