Why events can't be used in the same way in derived classes as in the base class in C#?

Question

In following code, I want to extend the behaviour of a class by deriving/subclassing it, and make use of an event of the base class:

public class A
{
    pub         


        

Answer 1

The standard practice here is to have a protected virtual method OnSomeEvent on your base class, then call that method in derived classes. Also, for threading reasons you will want to keep a reference to the handler before checking null and calling it.

For an explanation of the why read Jon Skeet's answer or the C# specification which describes how the compiler automatically creates a private field.

Here is one possible work around.

public class A
{
    public event EventHandler SomeEvent;

    public void someMethod()
    {
        OnSomeEvent();
    }

    protected void OnSomeEvent()
    {
        EventHandler handler = SomeEvent;
        if(handler != null)
            handler(this, someArgs);
    }
}

public class B : A
{
    public void someOtherMethod()
    {
        OnSomeEvent();
    }
}

Edit: Updated code based upon Framework Design Guidelines section 5.4 and reminders by others.