simplely speaking,Event in C# is that as one instance does one behaviour, it will receive the message and then react with the message.
2.Event Happening&Re-acting Mechanism
3.how to declare a Event
i.first declare a delegte
ii.secondly declare repective Event
like the following codes:
public delegate void MyNewEvent(|object sender|,|MyEventArgs e|);
public event MyNewEvent OnMyNewEvent;
4.Event Demo project
E.g. Cat& Mouse problem.
A mouse wanna steal something, at the same time, A cat is tracking him. Once the mouse is stealing , it will touch something and make noise. and then, the cat will know the mouse is stealing and receive the message and re-act at once. please create a project to realiaze this schema.
the codes are following:
namespace CatMouse
{
public class mouse
{
public delegate void MouseSteel(string food);
public event MouseSteel OnMouseSteel; //declare an Event
public void MouseIsSteeling(string food)
{
Console.WriteLine("Sender side: I am a mouse , I am steeling {0}\n", food);
if (OnMouseSteel != null)
//if there exists a listener who is listen to this event, OnMouseSteel object will not be null; else it will be null;
OnMouseSteel(food);
}
}
public class cat
{
public cat(mouse tmp_mouse)
{
this.A_mouse = tmp_mouse;
A_mouse.OnMouseSteel += new mouse.MouseSteel(A_mouse_OnMouseSteel);
// once the mouse is stealing, the cat will re-act by method <A_mouse_OnMouseSteel>
}
void A_mouse_OnMouseSteel(string food)
{
Console.WriteLine("Receiver side: Cat ! A mouse is steeling {0}\n", food);
}
private mouse A_mouse;
}
class Program
{
static void Main(string[] args)
{
mouse A_mouse=new mouse();
cat A_cat = new cat(A_mouse);
A_mouse.MouseIsSteeling("bread");
A_mouse.MouseIsSteeling("fish");
A_mouse.MouseIsSteeling("milk");
A_mouse.MouseIsSteeling("butter");
Console.Read();
}
}
}
and if everything works well, we will such window:
congratulations! :)