一般性地引发和处理事件

Posted 2021-02-26

For a discussion of .NET events best-practices, see [Roy Osherove's blog post](http://weblogs.asp.net/rosherove/articles/DefensiveEventPublishing.aspx) and [this post](http://blogs.msdn.com/ericlippert/archive/2009/04/29/events-and-races.aspx). Be sure to read the comments sections for some good arguments for and against the presented methods. Also, there is a good [MSDN Magazine article on Event Accessors](http://msdn.microsoft.com/en-us/magazine/cc163533.aspx), which may be useful.

Used in "Empire." The example shows an EventArgs with a DateTime object, but it could be a string or enumeration or whatever.

/// <summary>
/// Generic EventArgs class to hold event data.
/// </summary>
/// <example>
/// To create an event that sends a string (such as an error message):
/// <code>
/// public event EventHandler{EventArgs{string}} EventOccurred;
/// EventOccurred.Raise(sender, "The event occurred");
/// </code>
/// </example>
/// <see cref="http://geekswithblogs.net/HouseOfBilz/archive/2009/02/15/re-thinking-c-events.aspx"/>
/// <typeparam name="T">Any data</typeparam>
public class EventArgs<T> : EventArgs
{
    public T Args { get; private set; }
    public EventArgs(T args)
    {
        Args = args;
    }
    public override string ToString()
    {
        return Args.ToString();
    }
}
    /// <summary>
    /// Tell subscribers, if any, that this event has been raised.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="handler">The generic event handler</param>
    /// <param name="sender">this or null, usually</param>
    /// <param name="args">Whatever you want sent</param>
    public static void Raise<T>(this EventHandler<EventArgs<T>> handler, object sender, T args)
    {
        // Copy to temp var to be thread-safe (taken from C# 3.0 Cookbook - don't know if it's true)
        EventHandler<EventArgs<T>> copy = handler;
        if (copy != null)
        {
            copy(sender, new EventArgs<T>(args));
        }
    }
 
class Tester
{
    public static event EventHandler<EventArgs<DateTime>> GetTime_Rcvd;
 
    static void Main()
    {
        GetTime_Rcvd.Raise(null, MyDateTime);
    }
}