asked on

Manually Raising An Event

How do you manually raise an event. For example I am trying to manually raise a timer event. I have tried the following code thinking it would work, but unfortuantly it does not

this.checkSite( this, new System.Timers.ElapsedEventArgs() )

Any thoughts on how I can trigger the timer event manually?

thanks
dl

ASKER CERTIFIED SOLUTION

CJ_S

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

saar2

CJ_S is right. You just call the event name to raise the event.

1. Before you do this, you should check that the event has subscribes by comparing it to null:

if ( this.MyEvent != null )
{
this.MyEvent (this, EventArgs.Empty);
}

2. It would be neater to use the static member of EventArgs (class Empty) instead of initializing an instance manually (using new).

3. Sometimes there is specific public method which raises the event. For example, the Button class has a method called Click that fires the event.

Good luck.

Saar Carmi
Israel .Net Developer
saar@bigfoot.com

larockd

ASKER

Saar / CJ

I had a question in regards to what you meant by checking to see that the even has subscribes? What exactly does that mean?

Also, when you say it would be neater to use the static method of EventArgs instead of creating a new instance. Did you mean neater in that it would be more efficient? Or just cleaner style of coding?

Also, the code everyonce suggested has a caveat that I am not sure how to deal with previously I had this

strLastCheckStatus = "Started - Waiting" ;
// Update Listview
myListView.Items[ iListViewIndex ].SubItems[9].Text = strLastCheckStatus ;

if ( DateTime.Now >= dtNextCheck )
{
//Manually Raise The Check Site
Console.WriteLine("yup better check site") ;
}

Now when this ran before I raised the event manually the listview properly updated with the above status of "Waiting" Once I added the following to raise the event after the manually raise event comment

this.checkSite( this, new System.EventArgs() ) ;

The ListView No Longer Updates with The "Started - Waiting" status...

Anythoughts on why? Because I am asking another question in a question I will bump up the points.

Darrell

saar2

Each event has it's subscribers - those object instances that are doing to be notifed when the event is fired.

Before anyone subscribe to the event (using += operator in C#), the event value is Null and if you try to fire it - you'll get NullReferenceException.

The static method just calls the new operator - it's only a matter of cleaner code.

For your new problem, try to call Application.DoEvents
before you raise the event.

Good luck

larockd

ASKER

I am unable to find the static method for the System.EventArg() class. The only static method is empty

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemeventargsclassctortopic.asp

What am I missing?

dl

saar2

I meant to the Empty property (it's not method but a property - my mistake)

This property value is just an instance of the EventArgs.

Saar

larockd

ASKER

Thanks for the help, I am having the moderators split the points between both saar2 and CJ. Thx again.

dl

ComTech

Point total has been reduced to 50 points for a two way split.

50=CJ_S
50=saar2

I shall accept one here, and create another question for saar2, in this same Topic Area.

Regards,
ComTech
CS Admin @ EE

ComTech

saar2, Ihave left your points for the split here: https://www.experts-exchange.com/jsp/qManageQuestion.jsp?ta=c_sharp&qid=20314855

Thanks to all,
CT