using System.Runtime.InteropServices;
namespace System
{
// Summary: Represents the base class for
classes that contain event data,
// and provides a value to use for events that do not include event data.
[ComVisible(true)]
public class EventArgs
{
// Summary:
Provides a value to use with events that do not have event data.
public static readonly EventArgs Empty;
// Summary:Initializes
a new instance of the System.EventArgs class.
public EventArgs();
}
}
class WaterTankEventArgs : EventArgs
{
public enum Threshold { caution = 75, warning = 85,
danger = 95 }
public Threshold Message { get; private set; }
public int Level { get; private set; }
public WaterTankEventArgs(int Level, int
Capacity)
{
this.Level = Level;
if ((double)Threshold.danger / 100.0 * Capacity <=
Level)
Message = Threshold.danger;
else if ((double)Threshold.warning / 100.0 * Capacity <= Level)
Message = Threshold.warning;
else if ((double)Threshold.caution / 100.0 * Capacity <= Level)
Message = Threshold.caution;
}
}
- 75 is caution
- 85 is warning
- 95 is danger
we have properties to expose values of interest via message and level then we have a constructor that decides what kind of message to return to the user.
next we modify our watertank class slightly
class WaterTank
{
public int Capacity
{ get; private set; }
public int
CurrentLevel { get; private set; }
public EventHandler<WaterTankEventArgs> OverflowEventHandler { get; set; }
public WaterTank(int
MaxLiters)
{
this.Capacity = MaxLiters;
}
public void
IncreaseLevel(int Liters)
{
CurrentLevel += Liters;
//if we go over
the capacity there's an overflow
if (OverflowEventHandler != null && Capacity / CurrentLevel * 100 >= 75)
OverflowEventHandler.Invoke(this,new WaterTankEventArgs(CurrentLevel, Capacity));
}
}
now our main really didn't change all that much if we look at it
class Program
{
static void Main(string[] args)
{
char selection;
var wt = new WaterTank(50);
//define and
subscribe event
wt.OverflowEventHandler += (s, e) =>
Console.WriteLine($"{e.Message.ToString("g")} water level at {e.Level} liters");
do
{
Console.WriteLine("\n1)Add to tank\n2)check
current level\n0)exit");
switch (selection = Console.ReadKey().KeyChar)
{
case '1':
Console.WriteLine("\nhow many liters to add? ");
int l = 0;
int.TryParse(Console.ReadLine(), out l);
wt.IncreaseLevel(l);
break;
case '2':
Console.WriteLine($"\nWater Tank level {wt.CurrentLevel}");
break;
default:
Console.WriteLine("No such command");
break;
}
} while (selection != '0');
}
}
