Event pattern
In this chapter you will learn:
C# standard event pattern
C# has a standard event pattern.
It defines a standard class to accept the parameters for various events.
Event parameter should subclass System.EventArgs
to create its own event data.
public class ValueChangedEventArgs : System.EventArgs
{//from j a va2 s .c om
public readonly string str;
public ValueChangedEventArgs(string str)
{
this.str = str;
}
}
C# provides a generic delegate for the event handler.
public delegate void EventHandler<TEventArgs>(object source, TEventArgs e)
where TEventArgs : EventArgs;
We should follow the pattern when defining our own event handlers.
Example to use event pattern
using System;// j a v a2 s . c om
public class ValueChangedEventArgs : System.EventArgs
{
public readonly string str;
public ValueChangedEventArgs(string str)
{
this.str = str;
}
}
class Printer
{
public event EventHandler<ValueChangedEventArgs> ValuesChanged;
private string stringValue;
protected virtual void OnPriceChanged(ValueChangedEventArgs e)
{
if (ValuesChanged != null)
ValuesChanged(this, e);
}
public string StringValue
{
get
{
return stringValue;
}
set
{
OnPriceChanged(new ValueChangedEventArgs(value));
stringValue = value;
}
}
}
class Test
{
static void stock_PriceChanged(object sender, ValueChangedEventArgs e)
{
Console.WriteLine("event!");
}
static void Main()
{
Printer p = new Printer();
p.StringValue = "java2s.com";
}
}
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What you will learn in the next chapter:
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