EventArgs中的静态只读“ Empty”的目的是什么

Question

I'm new to C#, just a question on EventArgs class. We know the definition is :

public class EventArgs
{
   public static readonly EventArgs Empty;
   public EventArgs();
}

and I guess one of the use is when you don't care about passing custom information

public event EventHandler<EventArgs> TestHappening;

private void MyMethod()
{
    TestHappening( this, EventArgs.Empty );
}

but can't we achieve the same goal by using:

 TestHappening( this, new EventArgs() );

Answer 1

It's preferable to use EventArgs.Empty for two reasons:

1. Checking if arguments are empty is convenient

    EventArgs newArgs = new EventArgs(); EventArgs emptyArgs = EventArgs.Empty; Console.WriteLine(newArgs == EventArgs.Empty); // false Console.WriteLine(emptyArgs == EventArgs.Empty); // true 

2. No extra memory allocation because you essentially use the same class instance.

Answer 2

EventArgs.Empty is just define an instance of EventArgs without data. In C# there is a lot of class with defined property to declare a state or a kind or a value of this class to support who are just approach C#. string.Empty , int.MaxValue , etc are example for this